linux-stable.git/tools/sched_ext, branch v6.12

sched_ext: Update scx_show_state.py to match scx_ops_bypass_depth's new type

2024-11-05T21:45:27+00:00

0e7ffff1b811 ("scx: Fix raciness in scx_ops_bypass()") converted
scx_ops_bypass_depth from an atomic to an int. Update scx_show_state.py
accordingly.

Signed-off-by: Tejun Heo 
Fixes: 0e7ffff1b811 ("scx: Fix raciness in scx_ops_bypass()")

sched_ext: Make cast_mask() inline

2024-10-25T22:19:44+00:00

cast_mask() doesn't do any actual work and is defined in a header file.
Force it to be inline. When it is not inlined and the function is not used,
it can cause verificaiton failures like the following:

  # tools/testing/selftests/sched_ext/runner -t minimal
  ===== START =====
  TEST: minimal
  DESCRIPTION: Verify we can load a fully minimal scheduler
  OUTPUT:
  libbpf: prog 'cast_mask': missing BPF prog type, check ELF section name '.text'
  libbpf: prog 'cast_mask': failed to load: -22
  libbpf: failed to load object 'minimal'
  libbpf: failed to load BPF skeleton 'minimal': -22
  ERR: minimal.c:20
  Failed to open and load skel
  not ok 1 minimal #
  =====  END  =====

Signed-off-by: Tejun Heo 
Fixes: a748db0c8c6a ("tools/sched_ext: Receive misc updates from SCX repo")

sched_ext, scx_qmap: Add and use SCX_ENQ_CPU_SELECTED

2024-10-07T20:16:18+00:00

scx_qmap and other schedulers in the SCX repo are using SCX_ENQ_WAKEUP to
tell whether ops.select_cpu() was called. This is incorrect as
ops.select_cpu() can be skipped in the wakeup path and leads to e.g.
incorrectly skipping direct dispatch for tasks that are bound to a single
CPU.

sched core has been updated to specify ENQUEUE_RQ_SELECTED if
->select_task_rq() was called. Map it to SCX_ENQ_CPU_SELECTED and update
scx_qmap to test it instead of SCX_ENQ_WAKEUP.

Signed-off-by: Tejun Heo 
Acked-by: David Vernet 
Cc: Daniel Hodges 
Cc: Changwoo Min 
Cc: Andrea Righi 
Cc: Dan Schatzberg

sched_ext: Add __weak markers to BPF helper function decalarations

2024-10-02T16:53:12+00:00

Fix build errors by adding __weak markers to BPF helper function
declarations in header files. This resolves static assertion failures
in scx_qmap.bpf.c and scx_flatcg.bpf.c where functions like
scx_bpf_dispatch_from_dsq_set_slice, scx_bpf_dispatch_from_dsq_set_vtime,
and scx_bpf_task_cgroup were missing the __weak attribute.

[1] https://lore.kernel.org/all/ZvvfUqRNM4-jYQzH@linux.ibm.com

Signed-off-by: Vishal Chourasia 
Signed-off-by: Tejun Heo

scx_flatcg: Use a user DSQ for fallback instead of SCX_DSQ_GLOBAL

2024-09-26T22:56:46+00:00

scx_flatcg was using SCX_DSQ_GLOBAL for fallback handling. However, it is
assuming that SCX_DSQ_GLOBAL isn't automatically consumed, which was true a
while ago but is no longer the case. Also, there are further changes planned
for SCX_DSQ_GLOBAL which will disallow explicit consumption from it. Switch
to a user DSQ for fallback.

Signed-off-by: Tejun Heo 
Acked-by: David Vernet

tools/sched_ext: Receive misc updates from SCX repo

2024-09-25T22:22:37+00:00

Receive misc tools/sched_ext updates from https://github.com/sched-ext/scx
to sync userspace bits.

- LSP macros to help language servers.

- bpf_cpumask_weight() declaration and cast_mask() helper.

- Cosmetic updates to scx_flatcg.bpf.c.

Signed-off-by: Tejun Heo

sched_ext: Add __COMPAT helpers for features added during v6.12 devel cycle

2024-09-25T21:58:44+00:00

cgroup support and scx_bpf_dispatch[_vtime]_from_dsq() are newly added since
8bb30798fd6e ("sched_ext: Fixes incorrect type in bpf_scx_init()") which is
the current earliest commit targeted by BPF schedulers. Add compat helpers
for them and apply them in the example schedulers.

These will be dropped after a few kernel releases. The exact backward
compatibility window hasn't been decided yet.

Signed-off-by: Tejun Heo

sched_ext: Provide a sysfs enable_seq counter

2024-09-23T16:53:02+00:00

As discussed during the distro-centric session within the sched_ext
Microconference at LPC 2024, introduce a sequence counter that is
incremented every time a BPF scheduler is loaded.

This feature can help distributions in diagnosing potential performance
regressions by identifying systems where users are running (or have ran)
custom BPF schedulers.

Example:

 arighi@virtme-ng~> cat /sys/kernel/sched_ext/enable_seq
 0
 arighi@virtme-ng~> sudo scx_simple
 local=1 global=0
 ^CEXIT: unregistered from user space
 arighi@virtme-ng~> cat /sys/kernel/sched_ext/enable_seq
 1

In this way user-space tools (such as Ubuntu's apport and similar) are
able to gather and include this information in bug reports.

Cc: Giovanni Gherdovich 
Cc: Kleber Sacilotto de Souza 
Cc: Marcelo Henrique Cerri 
Cc: Phil Auld 
Signed-off-by: Andrea Righi 
Signed-off-by: Tejun Heo

scx_qmap: Implement highpri boosting

2024-09-09T23:42:47+00:00

Implement a silly boosting mechanism for nice -20 tasks. The only purpose is
demonstrating and testing scx_bpf_dispatch_from_dsq(). The boosting only
works within SHARED_DSQ and makes only minor differences with increased
dispatch batch (-b).

This exercises moving tasks to a user DSQ and all local DSQs from
ops.dispatch() and BPF timerfn.

v2: - Updated to use scx_bpf_dispatch_from_dsq_set_{slice|vtime}().

    - Drop the workaround for the iterated tasks not being trusted by the
      verifier. The issue is fixed from BPF side.

Signed-off-by: Tejun Heo 
Cc: Daniel Hodges 
Cc: David Vernet 
Cc: Changwoo Min 
Cc: Andrea Righi 
Cc: Dan Schatzberg

sched_ext: Implement scx_bpf_dispatch[_vtime]_from_dsq()

2024-09-09T23:42:47+00:00

Once a task is put into a DSQ, the allowed operations are fairly limited.
Tasks in the built-in local and global DSQs are executed automatically and,
ignoring dequeue, there is only one way a task in a user DSQ can be
manipulated - scx_bpf_consume() moves the first task to the dispatching
local DSQ. This inflexibility sometimes gets in the way and is an area where
multiple feature requests have been made.

Implement scx_bpf_dispatch[_vtime]_from_dsq(), which can be called during
DSQ iteration and can move the task to any DSQ - local DSQs, global DSQ and
user DSQs. The kfuncs can be called from ops.dispatch() and any BPF context
which dosen't hold a rq lock including BPF timers and SYSCALL programs.

This is an expansion of an earlier patch which only allowed moving into the
dispatching local DSQ:

  http://lkml.kernel.org/r/Zn4Cw4FDTmvXnhaf@slm.duckdns.org

v2: Remove @slice and @vtime from scx_bpf_dispatch_from_dsq[_vtime]() as
    they push scx_bpf_dispatch_from_dsq_vtime() over the kfunc argument
    count limit and often won't be needed anyway. Instead provide
    scx_bpf_dispatch_from_dsq_set_{slice|vtime}() kfuncs which can be called
    only when needed and override the specified parameter for the subsequent
    dispatch.

Signed-off-by: Tejun Heo 
Cc: Daniel Hodges 
Cc: David Vernet 
Cc: Changwoo Min 
Cc: Andrea Righi 
Cc: Dan Schatzberg