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BPF schedulers that can't hold task_struct pointers (arena-backed ones in
particular) key tasks by pid. During exit, pid is released before the
task finishes passing through scheduler callbacks, so a dying task
becomes invisible to the BPF side mid-schedule. scx_qmap hits this: an
exiting task's dispatch callback can't recover its queue entry, stalling
dispatch until SCX_EXIT_ERROR_STALL.
Add a unique non-zero u64 p->scx.tid assigned at fork that survives the
full task lifetime including exit. scx_bpf_tid_to_task() looks up the
task; unlike bpf_task_from_pid(), it handles exiting tasks.
The lookup costs an rhashtable insert/remove under scx_tasks_lock, so
root schedulers opt in via SCX_OPS_TID_TO_TASK. Sub-schedulers that set
the flag to declare a dependency are rejected at attach if root didn't
opt in.
scx_qmap converted: keys tasks by tid and enables SCX_OPS_ENQ_EXITING.
Pre-patch it stalls within seconds under a non-leader-exec workload;
with the patch it runs cleanly.
v3: Warn on rhashtable_lookup_insert_fast() failure via new
scx_tid_hash_insert() helper (Cheng-Yang Chou).
v2: Guard scx_root deref in scx_bpf_tid_to_task() error path. The kfunc
is registered via scx_kfunc_set_any and reachable from tracing and
syscall programs when no scheduler is attached (Cheng-Yang Chou).
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
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Pull to receive 73bd1227787b ("rhashtable: Restore insecure_elasticity
toggle") as a dependency for upcoming patches that use
.insecure_elasticity = true on their rhashtables.
Signed-off-by: Tejun Heo <tj@kernel.org>
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scx_sched_hash is inserted into under scx_sched_lock (raw_spinlock_irq)
in scx_link_sched(). rhashtable's sync grow path calls get_random_u32()
and does a GFP_ATOMIC allocation; both acquire regular spinlocks, which
is unsafe under raw_spinlock_t. Set insecure_elasticity to skip the
sync grow.
v2:
- Dropped dsq_hash changes. Insertion is not under raw_spin_lock.
- Switched from no_sync_grow flag to insecure_elasticity.
Fixes: 25037af712eb ("sched_ext: Add rhashtable lookup for sub-schedulers")
Signed-off-by: Tejun Heo <tj@kernel.org>
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Take scx_qmap for example, when sub scheduler is attached, there is
'BPF sub-scheduler "qmap" enabled' message, but when detached, the log
is missing. Add a new function to do the log thing, it can be used by
both root scheduler and sub scheduler.
Signed-off-by: Zhao Mengmeng <zhaomengmeng@kylinos.cn>
Reviewed-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing updates from Steven Rostedt:
- Fix printf format warning for bprintf
sunrpc uses a trace_printk() that triggers a printf warning during
the compile. Move the __printf() attribute around for when debugging
is not enabled the warning will go away
- Remove redundant check for EVENT_FILE_FL_FREED in
event_filter_write()
The FREED flag is checked in the call to event_file_file() and then
checked again right afterward, which is unneeded
- Clean up event_file_file() and event_file_data() helpers
These helper functions played a different role in the past, but now
with eventfs, the READ_ONCE() isn't needed. Simplify the code a bit
and also add a warning to event_file_data() if the file or its data
is not present
- Remove updating file->private_data in tracing open
All access to the file private data is handled by the helper
functions, which do not use file->private_data. Stop updating it on
open
- Show ENUM names in function arguments via BTF in function tracing
When showing the function arguments when func-args option is set for
function tracing, if one of the arguments is found to be an enum,
show the name of the enum instead of its number
- Add new trace_call__##name() API for tracepoints
Tracepoints are enabled via static_branch() blocks, where when not
enabled, there's only a nop that is in the code where the execution
will just skip over it. When tracing is enabled, the nop is converted
to a direct jump to the tracepoint code. Sometimes more calculations
are required to be performed to update the parameters of the
tracepoint. In this case, trace_##name##_enabled() is called which is
a static_branch() that gets enabled only when the tracepoint is
enabled. This allows the extra calculations to also be skipped by the
nop:
if (trace_foo_enabled()) {
x = bar();
trace_foo(x);
}
Where the x=bar() is only performed when foo is enabled. The problem
with this approach is that there's now two static_branch() calls. One
for checking if the tracepoint is enabled, and then again to know if
the tracepoint should be called. The second one is redundant
Introduce trace_call__foo() that will call the foo() tracepoint
directly without doing a static_branch():
if (trace_foo_enabled()) {
x = bar();
trace_call__foo();
}
- Update various locations to use the new trace_call__##name() API
- Move snapshot code out of trace.c
Cleaning up trace.c to not be a "dump all", move the snapshot code
out of it and into a new trace_snapshot.c file
- Clean up some "%*.s" to "%*s"
- Allow boot kernel command line options to be called multiple times
Have options like:
ftrace_filter=foo ftrace_filter=bar ftrace_filter=zoo
Equal to:
ftrace_filter=foo,bar,zoo
- Fix ipi_raise event CPU field to be a CPU field
The ipi_raise target_cpus field is defined as a __bitmask(). There is
now a __cpumask() field definition. Update the field to use that
- Have hist_field_name() use a snprintf() and not a series of strcat()
It's safer to use snprintf() that a series of strcat()
- Fix tracepoint regfunc balancing
A tracepoint can define a "reg" and "unreg" function that gets called
before the tracepoint is enabled, and after it is disabled
respectively. But on error, after the "reg" func is called and the
tracepoint is not enabled, the "unreg" function is not called to tear
down what the "reg" function performed
- Fix output that shows what histograms are enabled
Event variables are displayed incorrectly in the histogram output
Instead of "sched.sched_wakeup.$var", it is showing
"$sched.sched_wakeup.var" where the '$' is in the incorrect location
- Some other simple cleanups
* tag 'trace-v7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (24 commits)
selftests/ftrace: Add test case for fully-qualified variable references
tracing: Fix fully-qualified variable reference printing in histograms
tracepoint: balance regfunc() on func_add() failure in tracepoint_add_func()
tracing: Rebuild full_name on each hist_field_name() call
tracing: Report ipi_raise target CPUs as cpumask
tracing: Remove duplicate latency_fsnotify() stub
tracing: Preserve repeated trace_trigger boot parameters
tracing: Append repeated boot-time tracing parameters
tracing: Remove spurious default precision from show_event_trigger/filter formats
cpufreq: Use trace_call__##name() at guarded tracepoint call sites
tracing: Remove tracing_alloc_snapshot() when snapshot isn't defined
tracing: Move snapshot code out of trace.c and into trace_snapshot.c
mm: damon: Use trace_call__##name() at guarded tracepoint call sites
btrfs: Use trace_call__##name() at guarded tracepoint call sites
spi: Use trace_call__##name() at guarded tracepoint call sites
i2c: Use trace_call__##name() at guarded tracepoint call sites
kernel: Use trace_call__##name() at guarded tracepoint call sites
tracepoint: Add trace_call__##name() API
tracing: trace_mmap.h: fix a kernel-doc warning
tracing: Pretty-print enum parameters in function arguments
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git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull runtime verification updates from Steven Rostedt:
- Refactor da_monitor header to share handlers across monitor types
No functional changes, only less code duplication.
- Add Hybrid Automata model class
Add a new model class that extends deterministic automata by adding
constraints on transitions and states. Those constraints can take
into account wall-clock time and as such allow RV monitor to make
assertions on real time. Add documentation and code generation
scripts.
- Add stall monitor as hybrid automaton example
Add a monitor that triggers a violation when a task is stalling as an
example of automaton working with real time variables.
- Convert the opid monitor to a hybrid automaton
The opid monitor can be heavily simplified if written as a hybrid
automaton: instead of tracking preempt and interrupt enable/disable
events, it can just run constraints on the preemption/interrupt
states when events like wakeup and need_resched verify.
- Add support for per-object monitors in DA/HA
Allow writing deterministic and hybrid automata monitors for generic
objects (e.g. any struct), by exploiting a hash table where objects
are saved. This allows to track more than just tasks in RV. For
instance it will be used to track deadline entities in deadline
monitors.
- Add deadline tracepoints and move some deadline utilities
Prepare the ground for deadline monitors by defining events and
exporting helpers.
- Add nomiss deadline monitor
Add first example of deadline monitor asserting all entities complete
before their deadline.
- Improve rvgen error handling
Introduce AutomataError exception class and better handle expected
exceptions while showing a backtrace for unexpected ones.
- Improve python code quality in rvgen
Refactor the rvgen generation scripts to align with python best
practices: use f-strings instead of %, use len() instead of
__len__(), remove semicolons, use context managers for file
operations, fix whitespace violations, extract magic strings into
constants, remove unused imports and methods.
- Fix small bugs in rvgen
The generator scripts presented some corner case bugs: logical error
in validating what a correct dot file looks like, fix an isinstance()
check, enforce a dot file has an initial state, fix type annotations
and typos in comments.
- rvgen refactoring
Refactor automata.py to use iterator-based parsing and handle
required arguments directly in argparse.
- Allow epoll in rtapp-sleep monitor
The epoll_wait call is now rt-friendly so it should be allowed in the
sleep monitor as a valid sleep method.
* tag 'trace-rv-v7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (32 commits)
rv: Allow epoll in rtapp-sleep monitor
rv/rvgen: fix _fill_states() return type annotation
rv/rvgen: fix unbound loop variable warning
rv/rvgen: enforce presence of initial state
rv/rvgen: extract node marker string to class constant
rv/rvgen: fix isinstance check in Variable.expand()
rv/rvgen: make monitor arguments required in rvgen
rv/rvgen: remove unused __get_main_name method
rv/rvgen: remove unused sys import from dot2c
rv/rvgen: refactor automata.py to use iterator-based parsing
rv/rvgen: use class constant for init marker
rv/rvgen: fix DOT file validation logic error
rv/rvgen: fix PEP 8 whitespace violations
rv/rvgen: fix typos in automata and generator docstring and comments
rv/rvgen: use context managers for file operations
rv/rvgen: remove unnecessary semicolons
rv/rvgen: replace __len__() calls with len()
rv/rvgen: replace % string formatting with f-strings
rv/rvgen: remove bare except clauses in generator
rv/rvgen: introduce AutomataError exception class
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext
Pull sched_ext updates from Tejun Heo:
- cgroup sub-scheduler groundwork
Multiple BPF schedulers can be attached to cgroups and the dispatch
path is made hierarchical. This involves substantial restructuring of
the core dispatch, bypass, watchdog, and dump paths to be
per-scheduler, along with new infrastructure for scheduler ownership
enforcement, lifecycle management, and cgroup subtree iteration
The enqueue path is not yet updated and will follow in a later cycle
- scx_bpf_dsq_reenq() generalized to support any DSQ including remote
local DSQs and user DSQs
Built on top of this, SCX_ENQ_IMMED guarantees that tasks dispatched
to local DSQs either run immediately or get reenqueued back through
ops.enqueue(), giving schedulers tighter control over queueing
latency
Also useful for opportunistic CPU sharing across sub-schedulers
- ops.dequeue() was only invoked when the core knew a task was in BPF
data structures, missing scheduling property change events and
skipping callbacks for non-local DSQ dispatches from ops.select_cpu()
Fixed to guarantee exactly one ops.dequeue() call when a task leaves
BPF scheduler custody
- Kfunc access validation moved from runtime to BPF verifier time,
removing runtime mask enforcement
- Idle SMT sibling prioritization in the idle CPU selection path
- Documentation, selftest, and tooling updates. Misc bug fixes and
cleanups
* tag 'sched_ext-for-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (134 commits)
tools/sched_ext: Add explicit cast from void* in RESIZE_ARRAY()
sched_ext: Make string params of __ENUM_set() const
tools/sched_ext: Kick home CPU for stranded tasks in scx_qmap
sched_ext: Drop spurious warning on kick during scheduler disable
sched_ext: Warn on task-based SCX op recursion
sched_ext: Rename scx_kf_allowed_on_arg_tasks() to scx_kf_arg_task_ok()
sched_ext: Remove runtime kfunc mask enforcement
sched_ext: Add verifier-time kfunc context filter
sched_ext: Drop redundant rq-locked check from scx_bpf_task_cgroup()
sched_ext: Decouple kfunc unlocked-context check from kf_mask
sched_ext: Fix ops.cgroup_move() invocation kf_mask and rq tracking
sched_ext: Track @p's rq lock across set_cpus_allowed_scx -> ops.set_cpumask
sched_ext: Add select_cpu kfuncs to scx_kfunc_ids_unlocked
sched_ext: Drop TRACING access to select_cpu kfuncs
selftests/sched_ext: Fix wrong DSQ ID in peek_dsq error message
sched_ext: Documentation: improve accuracy of task lifecycle pseudo-code
selftests/sched_ext: Improve runner error reporting for invalid arguments
sched_ext: Documentation: Fix scx_bpf_move_to_local kfunc name
sched_ext: Documentation: Add ops.dequeue() to task lifecycle
tools/sched_ext: Fix off-by-one in scx_sdt payload zeroing
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
"Fair scheduling updates:
- Skip SCHED_IDLE rq for SCHED_IDLE tasks (Christian Loehle)
- Remove superfluous rcu_read_lock() in the wakeup path (K Prateek Nayak)
- Simplify the entry condition for update_idle_cpu_scan() (K Prateek Nayak)
- Simplify SIS_UTIL handling in select_idle_cpu() (K Prateek Nayak)
- Avoid overflow in enqueue_entity() (K Prateek Nayak)
- Update overutilized detection (Vincent Guittot)
- Prevent negative lag increase during delayed dequeue (Vincent Guittot)
- Clear buddies for preempt_short (Vincent Guittot)
- Implement more complex proportional newidle balance (Peter Zijlstra)
- Increase weight bits for avg_vruntime (Peter Zijlstra)
- Use full weight to __calc_delta() (Peter Zijlstra)
RT and DL scheduling updates:
- Fix incorrect schedstats for rt and dl thread (Dengjun Su)
- Skip group schedulable check with rt_group_sched=0 (Michal Koutný)
- Move group schedulability check to sched_rt_global_validate()
(Michal Koutný)
- Add reporting of runtime left & abs deadline to sched_getattr()
for DEADLINE tasks (Tommaso Cucinotta)
Scheduling topology updates by K Prateek Nayak:
- Compute sd_weight considering cpuset partitions
- Extract "imb_numa_nr" calculation into a separate helper
- Allocate per-CPU sched_domain_shared in s_data
- Switch to assigning "sd->shared" from s_data
- Remove sched_domain_shared allocation with sd_data
Energy-aware scheduling updates:
- Filter false overloaded_group case for EAS (Vincent Guittot)
- PM: EM: Switch to rcu_dereference_all() in wakeup path
(Dietmar Eggemann)
Infrastructure updates:
- Replace use of system_unbound_wq with system_dfl_wq (Marco Crivellari)
Proxy scheduling updates by John Stultz:
- Make class_schedulers avoid pushing current, and get rid of proxy_tag_curr()
- Minimise repeated sched_proxy_exec() checking
- Fix potentially missing balancing with Proxy Exec
- Fix and improve task::blocked_on et al handling
- Add assert_balance_callbacks_empty() helper
- Add logic to zap balancing callbacks if we pick again
- Move attach_one_task() and attach_task() helpers to sched.h
- Handle blocked-waiter migration (and return migration)
- Add K Prateek Nayak to scheduler reviewers for proxy execution
Misc cleanups and fixes by John Stultz, Joseph Salisbury, Peter
Zijlstra, K Prateek Nayak, Michal Koutný, Randy Dunlap, Shrikanth
Hegde, Vincent Guittot, Zhan Xusheng, Xie Yuanbin and Vincent Guittot"
* tag 'sched-core-2026-04-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (46 commits)
sched/eevdf: Clear buddies for preempt_short
sched/rt: Cleanup global RT bandwidth functions
sched/rt: Move group schedulability check to sched_rt_global_validate()
sched/rt: Skip group schedulable check with rt_group_sched=0
sched/fair: Avoid overflow in enqueue_entity()
sched: Use u64 for bandwidth ratio calculations
sched/fair: Prevent negative lag increase during delayed dequeue
sched/fair: Use sched_energy_enabled()
sched: Handle blocked-waiter migration (and return migration)
sched: Move attach_one_task and attach_task helpers to sched.h
sched: Add logic to zap balance callbacks if we pick again
sched: Add assert_balance_callbacks_empty helper
sched/locking: Add special p->blocked_on==PROXY_WAKING value for proxy return-migration
sched: Fix modifying donor->blocked on without proper locking
locking: Add task::blocked_lock to serialize blocked_on state
sched: Fix potentially missing balancing with Proxy Exec
sched: Minimise repeated sched_proxy_exec() checking
sched: Make class_schedulers avoid pushing current, and get rid of proxy_tag_curr()
MAINTAINERS: Add K Prateek Nayak to scheduler reviewers
sched/core: Get this cpu once in ttwu_queue_cond()
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer core updates from Thomas Gleixner:
- A rework of the hrtimer subsystem to reduce the overhead for
frequently armed timers, especially the hrtick scheduler timer:
- Better timer locality decision
- Simplification of the evaluation of the first expiry time by
keeping track of the neighbor timers in the RB-tree by providing
a RB-tree variant with neighbor links. That avoids walking the
RB-tree on removal to find the next expiry time, but even more
important allows to quickly evaluate whether a timer which is
rearmed changes the position in the RB-tree with the modified
expiry time or not. If not, the dequeue/enqueue sequence which
both can end up in rebalancing can be completely avoided.
- Deferred reprogramming of the underlying clock event device. This
optimizes for the situation where a hrtimer callback sets the
need resched bit. In that case the code attempts to defer the
re-programming of the clock event device up to the point where
the scheduler has picked the next task and has the next hrtick
timer armed. In case that there is no immediate reschedule or
soft interrupts have to be handled before reaching the reschedule
point in the interrupt entry code the clock event is reprogrammed
in one of those code paths to prevent that the timer becomes
stale.
- Support for clocksource coupled clockevents
The TSC deadline timer is coupled to the TSC. The next event is
programmed in TSC time. Currently this is done by converting the
CLOCK_MONOTONIC based expiry value into a relative timeout,
converting it into TSC ticks, reading the TSC adding the delta
ticks and writing the deadline MSR.
As the timekeeping core has the conversion factors for the TSC
already, the whole back and forth conversion can be completely
avoided. The timekeeping core calculates the reverse conversion
factors from nanoseconds to TSC ticks and utilizes the base
timestamps of TSC and CLOCK_MONOTONIC which are updated once per
tick. This allows a direct conversion into the TSC deadline value
without reading the time and as a bonus keeps the deadline
conversion in sync with the TSC conversion factors, which are
updated by adjtimex() on systems with NTP/PTP enabled.
- Allow inlining of the clocksource read and clockevent write
functions when they are tiny enough, e.g. on x86 RDTSC and WRMSR.
With all those enhancements in place a hrtick enabled scheduler
provides the same performance as without hrtick. But also other
hrtimer users obviously benefit from these optimizations.
- Robustness improvements and cleanups of historical sins in the
hrtimer and timekeeping code.
- Rewrite of the clocksource watchdog.
The clocksource watchdog code has over time reached the state of an
impenetrable maze of duct tape and staples. The original design,
which was made in the context of systems far smaller than today, is
based on the assumption that the to be monitored clocksource (TSC)
can be trivially compared against a known to be stable clocksource
(HPET/ACPI-PM timer).
Over the years this rather naive approach turned out to have major
flaws. Long delays between the watchdog invocations can cause wrap
arounds of the reference clocksource. The access to the reference
clocksource degrades on large multi-sockets systems dure to
interconnect congestion. This has been addressed with various
heuristics which degraded the accuracy of the watchdog to the point
that it fails to detect actual TSC problems on older hardware which
exposes slow inter CPU drifts due to firmware manipulating the TSC to
hide SMI time.
The rewrite addresses this by:
- Restricting the validation against the reference clocksource to
the boot CPU which is usually closest to the legacy block which
contains the reference clocksource (HPET/ACPI-PM).
- Do a round robin validation betwen the boot CPU and the other
CPUs based only on the TSC with an algorithm similar to the TSC
synchronization code during CPU hotplug.
- Being more leniant versus remote timeouts
- The usual tiny fixes, cleanups and enhancements all over the place
* tag 'timers-core-2026-04-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (75 commits)
alarmtimer: Access timerqueue node under lock in suspend
hrtimer: Fix incorrect #endif comment for BITS_PER_LONG check
posix-timers: Fix stale function name in comment
timers: Get this_cpu once while clearing the idle state
clocksource: Rewrite watchdog code completely
clocksource: Don't use non-continuous clocksources as watchdog
x86/tsc: Handle CLOCK_SOURCE_VALID_FOR_HRES correctly
MIPS: Don't select CLOCKSOURCE_WATCHDOG
parisc: Remove unused clocksource flags
hrtimer: Add a helper to retrieve a hrtimer from its timerqueue node
hrtimer: Remove trailing comma after HRTIMER_MAX_CLOCK_BASES
hrtimer: Mark index and clockid of clock base as const
hrtimer: Drop unnecessary pointer indirection in hrtimer_expire_entry event
hrtimer: Drop spurious space in 'enum hrtimer_base_type'
hrtimer: Don't zero-initialize ret in hrtimer_nanosleep()
hrtimer: Remove hrtimer_get_expires_ns()
timekeeping: Mark offsets array as const
timekeeping/auxclock: Consistently use raw timekeeper for tk_setup_internals()
timer_list: Print offset as signed integer
tracing: Use explicit array size instead of sentinel elements in symbol printing
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git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull power management updates from Rafael Wysocki:
"Once again, cpufreq is the most active development area, mostly
because of the new feature additions and documentation updates in the
amd-pstate driver, but there are also changes in the cpufreq core
related to boost support and other assorted updates elsewhere.
Next up are power capping changes due to the major cleanup of the
Intel RAPL driver.
On the cpuidle front, a new C-states table for Intel Panther Lake is
added to the intel_idle driver, the stopped tick handling in the menu
and teo governors is updated, and there are a couple of cleanups.
Apart from the above, support for Tegra114 is added to devfreq and
there are assorted cleanups of that code, there are also two updates
of the operating performance points (OPP) library, two minor updates
related to hibernation, and cpupower utility man pages updates and
cleanups.
Specifics:
- Update qcom-hw DT bindings to include Eliza hardware (Abel Vesa)
- Update cpufreq-dt-platdev blocklist (Faruque Ansari)
- Minor updates to driver and dt-bindings for Tegra (Thierry Reding,
Rosen Penev)
- Add MAINTAINERS entry for CPPC driver (Viresh Kumar)
- Add support for new features: CPPC performance priority, Dynamic
EPP, Raw EPP, and new unit tests for them to amd-pstate (Gautham
Shenoy, Mario Limonciello)
- Fix sysfs files being present when HW missing and broken/outdated
documentation in the amd-pstate driver (Ninad Naik, Gautham Shenoy)
- Pass the policy to cpufreq_driver->adjust_perf() to avoid using
cpufreq_cpu_get() in the .adjust_perf() callback in amd-pstate
which leads to a scheduling-while-atomic bug (K Prateek Nayak)
- Clean up dead code in Kconfig for cpufreq (Julian Braha)
- Remove max_freq_req update for pre-existing cpufreq policy and add
a boost_freq_req QoS request to save the boost constraint instead
of overwriting the last scaling_max_freq constraint (Pierre
Gondois)
- Embed cpufreq QoS freq_req objects in cpufreq policy so they all
are allocated in one go along with the policy to simplify lifetime
rules and avoid error handling issues (Viresh Kumar)
- Use DMI max speed when CPPC is unavailable in the acpi-cpufreq
scaling driver (Henry Tseng)
- Switch policy_is_shared() in cpufreq to using cpumask_nth() instead
of cpumask_weight() because the former is more efficient (Yury
Norov)
- Use sysfs_emit() in sysfs show functions for cpufreq governor
attributes (Thorsten Blum)
- Update intel_pstate to stop returning an error when "off" is
written to its status sysfs attribute while the driver is already
off (Fabio De Francesco)
- Include current frequency in the debug message printed by
__cpufreq_driver_target() (Pengjie Zhang)
- Refine stopped tick handling in the menu cpuidle governor and
rearrange stopped tick handling in the teo cpuidle governor (Rafael
Wysocki)
- Add Panther Lake C-states table to the intel_idle driver (Artem
Bityutskiy)
- Clean up dead dependencies on CPU_IDLE in Kconfig (Julian Braha)
- Simplify cpuidle_register_device() with guard() (Huisong Li)
- Use performance level if available to distinguish between rates in
OPP debugfs (Manivannan Sadhasivam)
- Fix scoped_guard in dev_pm_opp_xlate_required_opp() (Viresh Kumar)
- Return -ENODATA if the snapshot image is not loaded (Alberto
Garcia)
- Remove inclusion of crypto/hash.h from hibernate_64.c on x86 (Eric
Biggers)
- Clean up and rearrange the intel_rapl power capping driver to make
the respective interface drivers (TPMI, MSR, and MMOI) hold their
own settings and primitives and consolidate PL4 and PMU support
flags into rapl_defaults (Kuppuswamy Sathyanarayanan)
- Correct kernel-doc function parameter names in the power capping
core code (Randy Dunlap)
- Remove unneeded casting for HZ_PER_KHZ in devfreq (Andy Shevchenko)
- Use _visible attribute to replace create/remove_sysfs_files() in
devfreq (Pengjie Zhang)
- Add Tegra114 support to activity monitor device in tegra30-devfreq
as a preparation to upcoming EMC controller support (Svyatoslav
Ryhel)
- Fix mistakes in cpupower man pages, add the boost and epp options
to the cpupower-frequency-info man page, and add the perf-bias
option to the cpupower-info man page (Roberto Ricci)
- Remove unnecessary extern declarations from getopt.h in arguments
parsing functions in cpufreq-set, cpuidle-info, cpuidle-set,
cpupower-info, and cpupower-set utilities (Kaushlendra Kumar)"
* tag 'pm-7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (74 commits)
cpufreq/amd-pstate: Add POWER_SUPPLY select for dynamic EPP
cpupower: remove extern declarations in cmd functions
cpuidle: Simplify cpuidle_register_device() with guard()
PM / devfreq: tegra30-devfreq: add support for Tegra114
PM / devfreq: use _visible attribute to replace create/remove_sysfs_files()
PM / devfreq: Remove unneeded casting for HZ_PER_KHZ
MAINTAINERS: amd-pstate: Step down as maintainer, add Prateek as reviewer
cpufreq: Pass the policy to cpufreq_driver->adjust_perf()
cpufreq/amd-pstate: Pass the policy to amd_pstate_update()
cpufreq/amd-pstate-ut: Add a unit test for raw EPP
cpufreq/amd-pstate: Add support for raw EPP writes
cpufreq/amd-pstate: Add support for platform profile class
cpufreq/amd-pstate: add kernel command line to override dynamic epp
cpufreq/amd-pstate: Add dynamic energy performance preference
Documentation: amd-pstate: fix dead links in the reference section
cpufreq/amd-pstate: Cache the max frequency in cpudata
Documentation/amd-pstate: Add documentation for amd_pstate_floor_{freq,count}
Documentation/amd-pstate: List amd_pstate_prefcore_ranking sysfs file
Documentation/amd-pstate: List amd_pstate_hw_prefcore sysfs file
amd-pstate-ut: Add a testcase to validate the visibility of driver attributes
...
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to resolve the conflict with urgent fixes.
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kick_cpus_irq_workfn() warns when scx_kick_syncs is NULL, but this can
legitimately happen when a BPF timer or other kick source races with
free_kick_syncs() during scheduler disable. Drop the pr_warn_once() and
add a comment explaining the race.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Zhao Mengmeng <zhaomengmeng@kylinos.cn>
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The kf_tasks[] design assumes task-based SCX ops don't nest - if they
did, kf_tasks[0] would get clobbered. The old scx_kf_allow() WARN_ONCE
caught invalid nesting via kf_mask, but that machinery is gone now.
Add a WARN_ON_ONCE(current->scx.kf_tasks[0]) at the top of each
SCX_CALL_OP_TASK*() macro. Checking kf_tasks[0] alone is sufficient: all
three variants (SCX_CALL_OP_TASK, SCX_CALL_OP_TASK_RET,
SCX_CALL_OP_2TASKS_RET) write to kf_tasks[0], so a non-NULL value at
entry to any of the three means re-entry from somewhere in the family.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Andrea Righi <arighi@nvidia.com>
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The "kf_allowed" framing on this helper comes from the old runtime
scx_kf_allowed() gate, which has been removed. Rename it to describe what it
actually does in the new model.
Pure rename, no functional change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Andrea Righi <arighi@nvidia.com>
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Now that scx_kfunc_context_filter enforces context-sensitive kfunc
restrictions at BPF load time, the per-task runtime enforcement via
scx_kf_mask is redundant. Remove it entirely:
- Delete enum scx_kf_mask, the kf_mask field on sched_ext_entity, and
the scx_kf_allow()/scx_kf_disallow()/scx_kf_allowed() helpers along
with the higher_bits()/highest_bit() helpers they used.
- Strip the @mask parameter (and the BUILD_BUG_ON checks) from the
SCX_CALL_OP[_RET]/SCX_CALL_OP_TASK[_RET]/SCX_CALL_OP_2TASKS_RET
macros and update every call site. Reflow call sites that were
wrapped only to fit the old 5-arg form and now collapse onto a single
line under ~100 cols.
- Remove the in-kfunc scx_kf_allowed() runtime checks from
scx_dsq_insert_preamble(), scx_dsq_move(), scx_bpf_dispatch_nr_slots(),
scx_bpf_dispatch_cancel(), scx_bpf_dsq_move_to_local___v2(),
scx_bpf_sub_dispatch(), scx_bpf_reenqueue_local(), and the per-call
guard inside select_cpu_from_kfunc().
scx_bpf_task_cgroup() and scx_kf_allowed_on_arg_tasks() were already
cleaned up in the "drop redundant rq-locked check" patch.
scx_kf_allowed_if_unlocked() was rewritten in the preceding "decouple"
patch. No further changes to those helpers here.
Co-developed-by: Juntong Deng <juntong.deng@outlook.com>
Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
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Move enforcement of SCX context-sensitive kfunc restrictions from per-task
runtime kf_mask checks to BPF verifier-time filtering, using the BPF core's
struct_ops context information.
A shared .filter callback is attached to each context-sensitive BTF set
and consults a per-op allow table (scx_kf_allow_flags[]) indexed by SCX
ops member offset. Disallowed calls are now rejected at program load time
instead of at runtime.
The old model split reachability across two places: each SCX_CALL_OP*()
set bits naming its op context, and each kfunc's scx_kf_allowed() check
OR'd together the bits it accepted. A kfunc was callable when those two
masks overlapped. The new model transposes the result to the caller side -
each op's allow flags directly list the kfunc groups it may call. The old
bit assignments were:
Call-site bits:
ops.select_cpu = ENQUEUE | SELECT_CPU
ops.enqueue = ENQUEUE
ops.dispatch = DISPATCH
ops.cpu_release = CPU_RELEASE
Kfunc-group accepted bits:
enqueue group = ENQUEUE | DISPATCH
select_cpu group = SELECT_CPU | ENQUEUE
dispatch group = DISPATCH
cpu_release group = CPU_RELEASE
Intersecting them yields the reachability now expressed directly by
scx_kf_allow_flags[]:
ops.select_cpu -> SELECT_CPU | ENQUEUE
ops.enqueue -> SELECT_CPU | ENQUEUE
ops.dispatch -> ENQUEUE | DISPATCH
ops.cpu_release -> CPU_RELEASE
Unlocked ops carried no kf_mask bits and reached only unlocked kfuncs;
that maps directly to UNLOCKED in the new table.
Equivalence was checked by walking every (op, kfunc-group) combination
across SCX ops, SYSCALL, and non-SCX struct_ops callers against the old
scx_kf_allowed() runtime checks. With two intended exceptions (see below),
all combinations reach the same verdict; disallowed calls are now caught at
load time instead of firing scx_error() at runtime.
scx_bpf_dsq_move_set_slice() and scx_bpf_dsq_move_set_vtime() are
exceptions: they have no runtime check at all, but the new filter rejects
them from ops outside dispatch/unlocked. The affected cases are nonsensical
- the values these setters store are only read by
scx_bpf_dsq_move{,_vtime}(), which is itself restricted to
dispatch/unlocked, so a setter call from anywhere else was already dead
code.
Runtime scx_kf_mask enforcement is left in place by this patch and removed
in a follow-up.
Original-patch-by: Juntong Deng <juntong.deng@outlook.com>
Original-patch-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
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scx_kf_allowed_on_arg_tasks() runs both an scx_kf_allowed(__SCX_KF_RQ_LOCKED)
mask check and a kf_tasks[] check. After the preceding call-site fixes,
every SCX_CALL_OP_TASK*() invocation has kf_mask & __SCX_KF_RQ_LOCKED
non-zero, so the mask check is redundant whenever the kf_tasks[] check
passes. Drop it and simplify the helper to take only @sch and @p.
Fold the locking guarantee into the SCX_CALL_OP_TASK() comment block, which
scx_bpf_task_cgroup() now points to.
No functional change.
Extracted from a larger verifier-time kfunc context filter patch
originally written by Juntong Deng.
Original-patch-by: Juntong Deng <juntong.deng@outlook.com>
Cc: Cheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
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scx_kf_allowed_if_unlocked() uses !current->scx.kf_mask as a proxy for "no
SCX-tracked lock held". kf_mask is removed in a follow-up patch, so its two
callers - select_cpu_from_kfunc() and scx_dsq_move() - need another basis.
Add a new bool scx_rq.in_select_cpu, set across the SCX_CALL_OP_TASK_RET
that invokes ops.select_cpu(), to capture the one case where SCX itself
holds no lock but try_to_wake_up() holds @p's pi_lock. Together with
scx_locked_rq(), it expresses the same accepted-context set.
select_cpu_from_kfunc() needs a runtime test because it has to take
different locking paths depending on context. Open-code as a three-way
branch. The unlocked branch takes raw_spin_lock_irqsave(&p->pi_lock)
directly - pi_lock alone is enough for the fields the kfunc reads, and is
lighter than task_rq_lock().
scx_dsq_move() doesn't really need a runtime test - its accepted contexts
could be enforced at verifier load time. But since the runtime state is
already there and using it keeps the upcoming load-time filter simpler, just
write it the same way: (scx_locked_rq() || in_select_cpu) &&
!kf_allowed(DISPATCH).
scx_kf_allowed_if_unlocked() is deleted with the conversions.
No semantic change.
v2: s/No functional change/No semantic change/ - the unlocked path now acquires
pi_lock instead of the heavier task_rq_lock() (Andrea Righi).
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
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sched_move_task() invokes ops.cgroup_move() inside task_rq_lock(tsk), so
@p's rq lock is held. The SCX_CALL_OP_TASK invocation mislabels this:
- kf_mask = SCX_KF_UNLOCKED (== 0), claiming no lock is held.
- rq = NULL, so update_locked_rq() doesn't run and scx_locked_rq()
returns NULL.
Switch to SCX_KF_REST and pass task_rq(p), matching ops.set_cpumask()
from set_cpus_allowed_scx().
Three effects:
- scx_bpf_task_cgroup() becomes callable (was rejected by
scx_kf_allowed(__SCX_KF_RQ_LOCKED)). Safe; rq lock is held.
- scx_bpf_dsq_move() is now rejected (was allowed via the unlocked
branch). Calling it while holding an unrelated task's rq lock is
risky; rejection is correct.
- scx_bpf_select_cpu_*() previously took the unlocked branch in
select_cpu_from_kfunc() and called task_rq_lock(p, &rf), which
would deadlock against the already-held pi_lock. Now it takes the
locked-rq branch and is rejected with -EPERM via the existing
kf_allowed(SCX_KF_SELECT_CPU | SCX_KF_ENQUEUE) check. Latent
deadlock fix.
No in-tree scheduler is known to call any of these from ops.cgroup_move().
v2: Add Fixes: tag (Andrea Righi).
Fixes: 18853ba782be ("sched_ext: Track currently locked rq")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
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The SCX_CALL_OP_TASK call site passes rq=NULL incorrectly, leaving
scx_locked_rq() unset. Pass task_rq(p) instead so update_locked_rq()
reflects reality.
v2: Add Fixes: tag (Andrea Righi).
Fixes: 18853ba782be ("sched_ext: Track currently locked rq")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
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select_cpu_from_kfunc() has an extra scx_kf_allowed_if_unlocked() branch
that accepts calls from unlocked contexts and takes task_rq_lock() itself
- a "callable from unlocked" property encoded in the kfunc body rather
than in set membership. That's fine while the runtime check is the
authoritative gate, but the upcoming verifier-time filter uses set
membership as the source of truth and needs it to reflect every context
the kfunc may be called from.
Add the three select_cpu kfuncs to scx_kfunc_ids_unlocked so their full
set of callable contexts is captured by set membership. This follows the
existing dual-set convention used by scx_bpf_dsq_move{,_vtime} and
scx_bpf_dsq_move_set_{slice,vtime}, which are members of both
scx_kfunc_ids_dispatch and scx_kfunc_ids_unlocked.
While at it, add brief comments on each duplicate BTF_ID_FLAGS block
(including the pre-existing dsq_move ones) explaining the dual
membership.
No runtime behavior change: the runtime check in select_cpu_from_kfunc()
remains the authoritative gate until it is removed along with the rest
of the scx_kf_mask enforcement in a follow-up.
v2: Clarify dispatch-set comment to name scx_bpf_dsq_move*() explicitly so it
doesn't appear to cover scx_bpf_sub_dispatch() (Andrea Righi).
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
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The select_cpu kfuncs - scx_bpf_select_cpu_dfl(), scx_bpf_select_cpu_and()
and __scx_bpf_select_cpu_and() - take task_rq_lock() internally. Exposing
them via scx_kfunc_set_idle to BPF_PROG_TYPE_TRACING is unsafe: arbitrary
tracing contexts (kprobes, tracepoints, fentry, LSM) may run with @p's
pi_lock state unknown.
Move them out of scx_kfunc_ids_idle into a new scx_kfunc_ids_select_cpu
set registered only for STRUCT_OPS and SYSCALL.
Extracted from a larger verifier-time kfunc context filter patch
originally written by Juntong Deng.
Original-patch-by: Juntong Deng <juntong.deng@outlook.com>
Cc: Cheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
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next buddy should not prevent shorter slice preemption. Don't take buddy
into account when checking if shorter slice entity can preempt and clear it
if the entity with a shorter slice can preempt current.
Test on snapdragon rb5:
hackbench -T -p -l 16000000 -g 2 1> /dev/null &
hackbench runs in cgroup /test-A
cyclictest -t 1 -i 2777 -D 63 --policy=fair --mlock -h 20000 -q
cyclictest runs in cgroup /test-B
tip/sched/core tip/sched/core +this patch
cyclictest slice (ms) (default)2.8 8 8
hackbench slice (ms) (default)2.8 20 20
Total Samples | 22679 22595 22686
Average (us) | 84 94(-12%) 59( 37%)
Median (P50) (us) | 56 56( 0%) 56( 0%)
90th Percentile (us) | 64 65(- 2%) 63( 3%)
99th Percentile (us) | 1047 1273(-22%) 74( 94%)
99.9th Percentile (us) | 2431 4751(-95%) 663( 86%)
Maximum (us) | 4694 8655(-84%) 3934( 55%)
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260410132321.2897789-1-vincent.guittot@linaro.org
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Merge cpufreq updates for 7.1-rc1:
- Update qcom-hw DT bindings to include Eliza hardware (Abel Vesa)
- Update cpufreq-dt-platdev blocklist (Faruque Ansari)
- Minor updates to driver and dt-bindings for Tegra (Thierry Reding,
Rosen Penev)
- Add MAINTAINERS entry for CPPC driver (Viresh Kumar)
- Add support for new features: CPPC performance priority, Dynamic EPP,
Raw EPP, and new unit tests for them to amd-pstate (Gautham Shenoy,
Mario Limonciello)
- Fix sysfs files being present when HW missing and broken/outdated
documentation in the amd-pstate driver (Ninad Naik, Gautham Shenoy)
- Pass the policy to cpufreq_driver->adjust_perf() to avoid using
cpufreq_cpu_get() in the .adjust_perf() callback in amd-pstate which
leads to a scheduling-while-atomic bug (K Prateek Nayak)
- Clean up dead code in Kconfig for cpufreq (Julian Braha)
- Remove max_freq_req update for pre-existing cpufreq policy and add a
boost_freq_req QoS request to save the boost constraint instead of
overwriting the last scaling_max_freq constraint (Pierre Gondois)
- Embed cpufreq QoS freq_req objects in cpufreq policy so they all
are allocated in one go along with the policy to simplify lifetime
rules and avoid error handling issues (Viresh Kumar)
- Use DMI max speed when CPPC is unavailable in the acpi-cpufreq
scaling driver (Henry Tseng)
- Switch policy_is_shared() in cpufreq to using cpumask_nth() instead
of cpumask_weight() because the former is more efficient (Yury Norov)
- Use sysfs_emit() in sysfs show functions for cpufreq governor
attributes (Thorsten Blum)
- Update intel_pstate to stop returning an error when "off" is written
to its status sysfs attribute while the driver is already off (Fabio
De Francesco)
- Include current frequency in the debug message printed by
__cpufreq_driver_target() (Pengjie Zhang)
* pm-cpufreq: (38 commits)
cpufreq/amd-pstate: Add POWER_SUPPLY select for dynamic EPP
MAINTAINERS: amd-pstate: Step down as maintainer, add Prateek as reviewer
cpufreq: Pass the policy to cpufreq_driver->adjust_perf()
cpufreq/amd-pstate: Pass the policy to amd_pstate_update()
cpufreq/amd-pstate-ut: Add a unit test for raw EPP
cpufreq/amd-pstate: Add support for raw EPP writes
cpufreq/amd-pstate: Add support for platform profile class
cpufreq/amd-pstate: add kernel command line to override dynamic epp
cpufreq/amd-pstate: Add dynamic energy performance preference
Documentation: amd-pstate: fix dead links in the reference section
cpufreq/amd-pstate: Cache the max frequency in cpudata
Documentation/amd-pstate: Add documentation for amd_pstate_floor_{freq,count}
Documentation/amd-pstate: List amd_pstate_prefcore_ranking sysfs file
Documentation/amd-pstate: List amd_pstate_hw_prefcore sysfs file
amd-pstate-ut: Add a testcase to validate the visibility of driver attributes
amd-pstate-ut: Add module parameter to select testcases
amd-pstate: Introduce a tracepoint trace_amd_pstate_cppc_req2()
amd-pstate: Add sysfs support for floor_freq and floor_count
amd-pstate: Add support for CPPC_REQ2 and FLOOR_PERF
x86/cpufeatures: Add AMD CPPC Performance Priority feature.
...
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Provide a debugfs directory llc_balancing, and a knob named
"enabled" under it to allow the user to turn off and on the
cache aware scheduling at runtime.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/0aa56f7fc48db2f8f700cd1aa34dedd0ec88351b.1775065312.git.tim.c.chen@linux.intel.com
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Introduce sched_cache_present to enable cache aware scheduling for
multi LLCs NUMA node Cache-aware load balancing should only be
enabled if there are more than 1 LLCs within 1 NUMA node.
sched_cache_present is introduced to indicate whether this
platform supports this topology.
Test results:
The first test platform is a 2 socket Intel Sapphire Rapids with 30
cores per socket. The DRAM interleaving is enabled in the BIOS so it
essential has one NUMA node with two last level caches. There are 60
CPUs associated with each last level cache.
The second test platform is a AMD Genoa. There are 4 Nodes and 32 CPUs
per node. Each node has 2 CCXs and each CCX has 16 CPUs.
hackbench/schbench/netperf/stream/stress-ng/chacha20 were launched
on these two platforms.
[TL;DR]
Sappire Rapids:
hackbench shows significant improvement when the number of
different active threads is below the capacity of a LLC.
schbench shows limitted wakeup latency improvement.
ChaCha20-xiangshan(risc-v simulator) shows good throughput
improvement. No obvious difference was observed in
netperf/stream/stress-ng in Hmean.
Genoa:
Significant improvement is observed in hackbench when
the active number of threads is lower than the number
of CPUs within 1 LLC. On v2, Aaron reported improvement
of hackbench/redis when system is underloaded.
ChaCha20-xiangshan shows huge throughput improvement.
Phoronix has tested v1 and shows good improvements in 30+
cases[3]. No obvious difference was observed in
netperf/stream/stress-ng in Hmean.
Detail:
Due to length constraints, data without much difference with
baseline is not presented.
Sapphire Rapids:
[hackbench pipe]
================
case load baseline(std%) compare%( std%)
threads-pipe-10 1-groups 1.00 ( 1.22) +26.09 ( 1.10)
threads-pipe-10 2-groups 1.00 ( 4.90) +22.88 ( 0.18)
threads-pipe-10 4-groups 1.00 ( 2.07) +9.00 ( 3.49)
threads-pipe-10 8-groups 1.00 ( 8.13) +3.45 ( 3.62)
threads-pipe-16 1-groups 1.00 ( 2.11) +26.30 ( 0.08)
threads-pipe-16 2-groups 1.00 ( 15.13) -1.77 ( 11.89)
threads-pipe-16 4-groups 1.00 ( 4.37) +0.58 ( 7.99)
threads-pipe-16 8-groups 1.00 ( 2.88) +2.71 ( 3.50)
threads-pipe-2 1-groups 1.00 ( 9.40) +22.07 ( 0.71)
threads-pipe-2 2-groups 1.00 ( 9.99) +18.01 ( 0.95)
threads-pipe-2 4-groups 1.00 ( 3.98) +24.66 ( 0.96)
threads-pipe-2 8-groups 1.00 ( 7.00) +21.83 ( 0.23)
threads-pipe-20 1-groups 1.00 ( 1.03) +28.84 ( 0.21)
threads-pipe-20 2-groups 1.00 ( 4.42) +31.90 ( 3.15)
threads-pipe-20 4-groups 1.00 ( 9.97) +4.56 ( 1.69)
threads-pipe-20 8-groups 1.00 ( 1.87) +1.25 ( 0.74)
threads-pipe-4 1-groups 1.00 ( 4.48) +25.67 ( 0.78)
threads-pipe-4 2-groups 1.00 ( 9.14) +4.91 ( 2.08)
threads-pipe-4 4-groups 1.00 ( 7.68) +19.36 ( 1.53)
threads-pipe-4 8-groups 1.00 ( 10.79) +7.20 ( 12.20)
threads-pipe-8 1-groups 1.00 ( 4.69) +21.93 ( 0.03)
threads-pipe-8 2-groups 1.00 ( 1.16) +25.29 ( 0.65)
threads-pipe-8 4-groups 1.00 ( 2.23) -1.27 ( 3.62)
threads-pipe-8 8-groups 1.00 ( 4.65) -3.08 ( 2.75)
Note: The default number of fd in hackbench is changed from 20 to various
values to ensure that threads fit within a single LLC, especially on AMD
systems. Take "threads-pipe-8, 2-groups" for example, the number of fd
is 8, and 2 groups are created.
[schbench]
The 99th percentile wakeup latency shows some improvements when the
system is underload, while it does not bring much difference with
the increasing of system utilization.
99th Wakeup Latencies Base (mean std) Compare (mean std) Change
=========================================================================
thread=2 9.00(0.00) 9.00(1.73) 0.00%
thread=4 7.33(0.58) 6.33(0.58) +13.64%
thread=8 9.00(0.00) 7.67(1.15) +14.78%
thread=16 8.67(0.58) 8.67(1.53) 0.00%
thread=32 9.00(0.00) 7.00(0.00) +22.22%
thread=64 9.33(0.58) 9.67(0.58) -3.64%
thread=128 12.00(0.00) 12.00(0.00) 0.00%
[chacha20 on simulated risc-v]
baseline:
Host time spent: 67861ms
cache aware scheduling enabled:
Host time spent: 54441ms
Time reduced by 24%
Genoa:
[hackbench pipe]
The default number of fd is 20, which exceed the number of CPUs
in a LLC. So the fd is adjusted to 2, 4, 6, 8, 20 respectively.
Exclude the result with large run-to-run variance, 10% ~ 50%
improvement is observed when the system is underloaded:
[hackbench pipe]
================
case load baseline(std%) compare%( std%)
threads-pipe-2 1-groups 1.00 ( 2.89) +47.33 ( 1.20)
threads-pipe-2 2-groups 1.00 ( 3.88) +39.82 ( 0.61)
threads-pipe-2 4-groups 1.00 ( 8.76) +5.57 ( 13.10)
threads-pipe-20 1-groups 1.00 ( 4.61) +11.72 ( 1.06)
threads-pipe-20 2-groups 1.00 ( 6.18) +14.55 ( 1.47)
threads-pipe-20 4-groups 1.00 ( 2.99) +10.16 ( 4.49)
threads-pipe-4 1-groups 1.00 ( 4.23) +43.70 ( 2.14)
threads-pipe-4 2-groups 1.00 ( 3.68) +8.45 ( 4.04)
threads-pipe-4 4-groups 1.00 ( 17.72) +2.42 ( 1.14)
threads-pipe-6 1-groups 1.00 ( 3.10) +7.74 ( 3.83)
threads-pipe-6 2-groups 1.00 ( 3.42) +14.26 ( 4.53)
threads-pipe-6 4-groups 1.00 ( 10.34) +10.94 ( 7.12)
threads-pipe-8 1-groups 1.00 ( 4.21) +9.06 ( 4.43)
threads-pipe-8 2-groups 1.00 ( 1.88) +3.74 ( 0.58)
threads-pipe-8 4-groups 1.00 ( 2.78) +23.96 ( 1.18)
[chacha20 on simulated risc-v]
Host time spent: 54762ms
Host time spent: 28295ms
Time reduced by 48%
Suggested-by: Libo Chen <libchen@purestorage.com>
Suggested-by: Adam Li <adamli@os.amperecomputing.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/71972e12ab4f08aff422b31e34df09bdbd94de84.1775065312.git.tim.c.chen@linux.intel.com
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During load balancing, make can_migrate_task()
consider a task's LLC preference.
Prevent a task from being moved out of its preferred LLC.
During the regular load balancing, if
the task cannot be migrated due to LLC locality, the
nr_balance_failed also should not be increased.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/53da65f3d59de31e1a1dc59a4093d8dd9d4dc206.1775065312.git.tim.c.chen@linux.intel.com
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Cache aware scheduling mainly does two things:
1. Prevent task from migrating out of its preferred LLC if not
nessasary.
2. Migrating task to their preferred LLC if nessasary.
For 1:
In the generic load balance, if the busiest runqueue has only one task,
active balancing may be invoked to move it away. However, this migration
might break LLC locality.
Prevent regular load balance from migrating a task that
prefers the current LLC. The load level and imbalance do not warrant
breaking LLC preference per the can_migrate_llc() policy. Here, the
benefit of LLC locality outweighs the power efficiency gained from
migrating the only runnable task away.
Before migration, check whether the task is running on its preferred
LLC: Do not move a lone task to another LLC if it would move the task
away from its preferred LLC or cause excessive imbalance between LLCs.
For 2:
On the other hand, if the migration type is migrate_llc_task, it means
that there are tasks on the env->src_cpu that want to be migrated to
their preferred LLC, launch the active load balance anyway.
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/9b816d8c27fabf2a9c0e1f61a6b90afe8ec4ad52.1775065312.git.tim.c.chen@linux.intel.com
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Introduce a new migration type, migrate_llc_task, to support
cache-aware load balancing.
After identifying the busiest sched_group (having the most tasks
preferring the destination LLC), mark migrations with this type.
During load balancing, each runqueue in the busiest sched_group is
examined, and the runqueue with the highest number of tasks preferring
the destination CPU is selected as the busiest runqueue.
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/b9df27c19cc5121ddb2a7d1be7f9d52fec1563dc.1775065312.git.tim.c.chen@linux.intel.com
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During LLC load balancing, first check for tasks that prefer the
destination LLC and balance them to it before others.
Mark source sched groups containing tasks preferring non local LLCs
with the group_llc_balance flag. This ensures the load balancer later
pulls or pushes these tasks toward their preferred LLCs.
The priority of group_llc_balance is lower than that of group_overloaded
and higher than that of all other group types. This is because
group_llc_balance may exacerbate load imbalance, and if the LLC balancing
attempt fails, the nr_balance_failed mechanism will trigger other group
types to rebalance the load.
The load balancer selects the busiest sched_group and migrates tasks
to less busy groups to distribute load across CPUs.
With cache-aware scheduling enabled, the busiest sched_group is
the one with most tasks preferring the destination LLC. If
the group has the llc_balance flag set, cache aware load balancing is
triggered.
Introduce the helper function update_llc_busiest() to identify the
sched_group with the most tasks preferring the destination LLC.
Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Suggested-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/baa458f45eab3f602af090c6d6af63dc864f5ec6.1775065312.git.tim.c.chen@linux.intel.com
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There is no need to check the local group twice for both
group_asym_packing and group_smt_balance. Adjust the code
to facilitate future checks for group types (cache-aware
load balancing) as well.
No functional changes are expected.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/99a57865c8ae1847087a5c00e92d24351cf3e5a8.1775065312.git.tim.c.chen@linux.intel.com
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During LLC load balancing, tabulate the number of tasks on each runqueue
that prefer the LLC contains the env->dst_cpu in a sched group.
For example, consider a system with 4 LLC sched groups (LLC0 to LLC3)
balancing towards LLC3. LLC0 has 3 tasks preferring LLC3, LLC1 has
2, and LLC2 has 1. LLC0, having the most tasks preferring LLC3, is
selected as the busiest source to pick tasks from.
Within a source LLC, the total number of tasks preferring a destination
LLC is computed by summing counts across all CPUs in that LLC. For
instance, if LLC0 has CPU0 with 2 tasks and CPU1 with 1 task preferring
LLC3, the total for LLC0 is 3.
These statistics allow the load balancer to choose tasks from source
sched groups that best match their preferred LLCs.
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/3d8502a33a753c4384b368f97f64ee70b1cea0db.1775065312.git.tim.c.chen@linux.intel.com
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Calculate the number of tasks' LLC preferences for each runqueue.
This statistic is computed during task enqueue and dequeue
operations, and is used by the cache-aware load balancing.
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/d15a64436d3acd19c5c53344c5e9d3d0b79b3233.1775065312.git.tim.c.chen@linux.intel.com
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The lowest level of sched domain for each CPU is assigned an
array where each element tracks the number of tasks preferring
a given LLC, indexed from 0 to max_lid. Since each CPU
has its dedicated sd, this implies that each CPU will have
a dedicated task LLC preference counter.
For example, sd->llc_counts[3] = 2 signifies that there
are 2 tasks on this runqueue which prefer to run within LLC3.
The load balancer can use this information to identify busy
runqueues and migrate tasks to their preferred LLC domains.
This array will be reallocated at runtime during sched domain
rebuild.
Introduce the buffer allocation mechanism, and the statistics
will be calculated in the subsequent patch.
Note: the LLC preference statistics of each CPU are reset on
sched domain rebuild and may under count temporarily, until the
CPU becomes idle and the count is cleared. This is a trade off
to avoid complex data synchronization across sched domain builds.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/42e79eceb8cd6be8a032401d481d101913bc5703.1775065312.git.tim.c.chen@linux.intel.com
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For each runqueue, track the number of tasks with an LLC preference
and how many of them are running on their preferred LLC. This mirrors
nr_numa_running and nr_preferred_running for NUMA balancing, and will
be used by cache-aware load balancing in later patches.
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/459a37102f3d74a4e09ea58401d2094ac731d044.1775065312.git.tim.c.chen@linux.intel.com
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With cache-aware scheduling enabled, each task is assigned a
preferred LLC ID. This allows quick identification of the LLC domain
where the task prefers to run, similar to numa_preferred_nid in
NUMA balancing.
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/f2ceecba5858680349ad4ce9303a2121f0bb7272.1775065312.git.tim.c.chen@linux.intel.com
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Introduce an index mapping between CPUs and their LLCs. This provides
a roughly continuous per LLC index needed for cache-aware load balancing in
later patches.
The existing per_cpu llc_id usually points to the first CPU of the
LLC domain, which is sparse and unsuitable as an array index. Using
llc_id directly would waste memory.
With the new mapping, CPUs in the same LLC share an approximate
continuous id:
per_cpu(llc_id, CPU=0...15) = 0
per_cpu(llc_id, CPU=16...31) = 1
per_cpu(llc_id, CPU=32...47) = 2
...
Note that the LLC IDs are allocated via bitmask, so the IDs may be
reused during CPU offline->online transitions.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Originally-by: K Prateek Nayak <kprateek.nayak@amd.com>
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/047ef46339e4db497b54a89940a7ebedf27fcf28.1775065312.git.tim.c.chen@linux.intel.com
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Cache-aware scheduling aggregates threads onto their preferred LLC,
mainly through load balancing. When the preferred LLC becomes
saturated, more threads are still placed there, increasing latency.
A mechanism is needed to limit aggregation so that the preferred LLC
does not become overloaded.
Introduce helper functions can_migrate_llc() and
can_migrate_llc_task() to enforce the LLC migration policy:
1. Aggregate a task to its preferred LLC if both source and
destination LLCs are not too busy, or if doing so will not
leave the preferred LLC much more imbalanced than the
non-preferred one (>20% utilization difference, a little
higher than the default imbalance_pct(17%) of the LLC domain
as hysteresis). Later this threshold will be turned into tunable
debugfs.
2. Allow moving a task from overloaded preferred LLC to a non
preferred LLC if this will not cause the non preferred LLC
to become too imbalanced to cause a later migration back.
3. If both LLCs are too busy, let the generic load balance to
spread the tasks.
Further (hysteresis)action could be taken in the future to prevent tasks
from being migrated into and out of the preferred LLC frequently (back and
forth): the threshold for migrating a task out of its preferred LLC should
be higher than that for migrating it into the LLC.
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/d19b52589cdceaee5e625980959f4d1982d6d7c9.1775065312.git.tim.c.chen@linux.intel.com
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decisions
When a system becomes busy and a process's preferred LLC is
saturated with too many threads, tasks within that LLC migrate
frequently. These in LLC migrations introduce latency and degrade
performance. To avoid this, task aggregation should be suppressed
when the preferred LLC is overloaded, which requires a metric to
indicate LLC utilization.
Record per LLC utilization/cpu capacity during periodic load
balancing. These statistics will be used in later patches to decide
whether tasks should be aggregated into their preferred LLC.
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/a48151b3d57f2a42a5971aaead1b7f81e69229f4.1775065312.git.tim.c.chen@linux.intel.com
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When NUMA balancing is enabled, the kernel currently iterates over all
online CPUs to aggregate process-wide occupancy data. On large systems,
this global scan introduces significant overhead.
To reduce scan latency, limit the search to a subset of relevant CPUs:
1. The task's preferred NUMA node.
2. The node where the task is currently running.
3. The node that contains the task's current preferred LLC..
While focusing solely on the preferred NUMA node is ideal, a
process-wide scan must remain flexible because the "preferred node"
is a per-task attribute. Different threads within the same process may
have different preferred nodes, causing the process-wide preference to
migrate. Maintaining a mask that covers both the preferred and active
running nodes ensures accuracy while significantly reducing the number of
CPUs inspected.
Future work may integrate numa_group to further refine task aggregation.
Suggested-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/57ed5fcec9b242803fe4ea2ce6e7f3de6a6efc6b.1775065312.git.tim.c.chen@linux.intel.com
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Adds infrastructure to enable cache-aware load balancing,
which improves cache locality by grouping tasks that share resources
within the same cache domain. This reduces cache misses and improves
overall data access efficiency.
In this initial implementation, threads belonging to the same process
are treated as entities that likely share working sets. The mechanism
tracks per-process CPU occupancy across cache domains and attempts to
migrate threads toward cache-hot domains where their process already
has active threads, thereby enhancing locality.
This provides a basic model for cache affinity. While the current code
targets the last-level cache (LLC), the approach could be extended to
other domain types such as clusters (L2) or node-internal groupings.
At present, the mechanism selects the CPU within an LLC that has the
highest recent runtime. Subsequent patches in this series will use this
information in the load-balancing path to guide task placement toward
preferred LLCs.
In the future, more advanced policies could be integrated through NUMA
balancing-for example, migrating a task to its preferred LLC when spare
capacity exists, or swapping tasks across LLCs to improve cache affinity.
Grouping of tasks could also be generalized from that of a process
to be that of a NUMA group, or be user configurable.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/6269a53221b9439b9ca00d18a9d1946fb64d8cff.1775065312.git.tim.c.chen@linux.intel.com
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The commit 5f6bd380c7bdb ("sched/rt: Remove default bandwidth control")
and followup changes made a few of the functions unnecessary, drop them
for simplicity.
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260323-sched-rert_groups-v3-3-1e7d5ed6b249@suse.com
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The sched_rt_global_constraints() function is a remnant that used to set
up global RT throttling but that is no more since commit 5f6bd380c7bdb
("sched/rt: Remove default bandwidth control") and the function ended up
only doing schedulability check.
Move the check into the validation function where it fits better.
(The order of validations sched_dl_global_validate() and
sched_rt_global_validate() shouldn't matter.)
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260323-sched-rert_groups-v3-2-1e7d5ed6b249@suse.com
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The warning from the commit 87f1fb77d87a6 ("sched: Add RT_GROUP WARN
checks for non-root task_groups") is wrong -- it assumes that only
task_groups with rt_rq are traversed, however, the schedulability check
would iterate all task_groups even when rt_group_sched=0 is disabled at
boot time but some non-root task_groups exist.
The schedulability check is supposed to validate:
a) that children don't overcommit its parent,
b) no RT task group overcommits global RT limit.
but with rt_group_sched=0 there is no (non-trivial) hierarchy of RT groups,
therefore skip the validation altogether. Otherwise, writes to the
global sched_rt_runtime_us knob will be rejected with incorrect
validation error.
This fix is immaterial with CONFIG_RT_GROUP_SCHED=n.
Fixes: 87f1fb77d87a6 ("sched: Add RT_GROUP WARN checks for non-root task_groups")
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260323-sched-rert_groups-v3-1-1e7d5ed6b249@suse.com
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John noted that commit 115135422562 ("sched/deadline: Fix 'stuck' dl_server")
unfixed the issue from commit a3a70caf7906 ("sched/deadline: Fix dl_server
behaviour").
The issue in commit 115135422562 was for wakeups of the server after the
deadline; in which case you *have* to start a new period. The case for
a3a70caf7906 is wakeups before the deadline.
Now, because the server is effectively running a least-laxity policy, it means
that any wakeup during the runnable phase means dl_entity_overflow() will be
true. This means we need to adjust the runtime to allow it to still run until
the existing deadline expires.
Use the revised wakeup rule for dl_defer entities.
Fixes: 115135422562 ("sched/deadline: Fix 'stuck' dl_server")
Reported-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Tested-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260404102244.GB22575@noisy.programming.kicks-ass.net
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Here is one scenario which was triggered when running:
stress-ng --yield=32 -t 10000000s&
while true; do perf bench sched messaging -p -t -l 100000 -g 16; done
on a 256CPUs machine after about an hour into the run:
__enqeue_entity: entity_key(-141245081754) weight(90891264) overflow_mul(5608800059305154560) vlag(57498) delayed?(0)
cfs_rq: zero_vruntime(3809707759657809) sum_w_vruntime(0) sum_weight(0) nr_queued(1)
cfs_rq->curr: entity_key(0) vruntime(3809707759657809) deadline(3809723966988476) weight(37)
The above comes from __enqueue_entity() after a place_entity(). Breaking
this down:
vlag_initial = 57498
vlag = (57498 * (37 + 90891264)) / 37 = 141,245,081,754
vruntime = 3809707759657809 - 141245081754 = 3,809,566,514,576,055
entity_key(se, cfs_rq) = -141,245,081,754
Now, multiplying the entity_key with its own weight results to
5,608,800,059,305,154,560 (same as what overflow_mul() suggests) but
in Python, without overflow, this would be: -1,2837,944,014,404,397,056
Avoid the overflow (without doing the division for avg_vruntime()), by moving
zero_vruntime to the new entity when it is heavier.
Fixes: 4823725d9d1d ("sched/fair: Increase weight bits for avg_vruntime")
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
[peterz: suggested 'weight > load' condition]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260407120052.GG3738010@noisy.programming.kicks-ass.net
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to_ratio() computes BW_SHIFT-scaled bandwidth ratios from u64 period and
runtime values, but it returns unsigned long. tg_rt_schedulable() also
stores the current group limit and the accumulated child sum in unsigned
long.
On 32-bit builds, large bandwidth ratios can be truncated and the RT
group sum can wrap when enough siblings are present. That can let an
overcommitted RT hierarchy pass the schedulability check, and it also
narrows the helper result for other callers.
Return u64 from to_ratio() and use u64 for the RT group totals so
bandwidth ratios are preserved and compared at full width on both 32-bit
and 64-bit builds.
Fixes: b40b2e8eb521 ("sched: rt: multi level group constraints")
Assisted-by: Codex:GPT-5
Signed-off-by: Joseph Salisbury <joseph.salisbury@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260403210014.2713404-1-joseph.salisbury@oracle.com
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar:
- Fix zero_vruntime tracking again (Peter Zijlstra)
- Fix avg_vruntime() usage in sched_debug (Peter Zijlstra)
* tag 'sched-urgent-2026-04-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/debug: Fix avg_vruntime() usage
sched/fair: Fix zero_vruntime tracking fix
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext
Pull sched_ext fixes from Tejun Heo:
"These are late but both fix subtle yet critical problems and the blast
radius is limited strictly to sched_ext.
- Fix stale direct dispatch state in ddsp_dsq_id which can cause
spurious warnings in mark_direct_dispatch() on task wakeup
- Fix is_bpf_migration_disabled() false negative on non-PREEMPT_RCU
configs which can lead to incorrectly dispatching migration-
disabled tasks to remote CPUs"
* tag 'sched_ext-for-7.0-rc6-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
sched_ext: Fix stale direct dispatch state in ddsp_dsq_id
sched_ext: Fix is_bpf_migration_disabled() false negative on non-PREEMPT_RCU
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Conflict in kernel/sched/ext.c between:
7e0ffb72de8a ("sched_ext: Fix stale direct dispatch state in
ddsp_dsq_id")
which clears ddsp state at individual call sites instead of
dispatch_enqueue(), and sub-sched related code reorg and API updates on
for-7.1. Resolved by applying the ddsp fix with for-7.1's signatures.
Signed-off-by: Tejun Heo <tj@kernel.org>
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