[ Upstream commit 1c6829cfd3d5124b125e6df41158665aea413b35 ]
Use the loop variable instead of the function argument to test the
other SMT siblings for idle.
Fixes: ff7db0bf24db ("sched/numa: Prefer using an idle CPU as a migration target instead of comparing tasks")
Signed-off-by: Mika Penttilä <mika.penttila@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Pankaj Gupta <pankaj.gupta@ionos.com>
Link: https://lkml.kernel.org/r/20210722063946.28951-1-mika.penttila@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 3a7956e25e1d7b3c148569e78895e1f3178122a9 upstream.
The kthread_is_per_cpu() construct relies on only being called on
PF_KTHREAD tasks (per the WARN in to_kthread). This gives rise to the
following usage pattern:
if ((p->flags & PF_KTHREAD) && kthread_is_per_cpu(p))
However, as reported by syzcaller, this is broken. The scenario is:
CPU0 CPU1 (running p)
(p->flags & PF_KTHREAD) // true
begin_new_exec()
me->flags &= ~(PF_KTHREAD|...);
kthread_is_per_cpu(p)
to_kthread(p)
WARN(!(p->flags & PF_KTHREAD) <-- *SPLAT*
Introduce __to_kthread() that omits the WARN and is sure to check both
values.
Use this to remove the problematic pattern for kthread_is_per_cpu()
and fix a number of other kthread_*() functions that have similar
issues but are currently not used in ways that would expose the
problem.
Notably kthread_func() is only ever called on 'current', while
kthread_probe_data() is only used for PF_WQ_WORKER, which implies the
task is from kthread_create*().
Fixes: ac687e6e8c26 ("kthread: Extract KTHREAD_IS_PER_CPU")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Link: https://lkml.kernel.org/r/YH6WJc825C4P0FCK@hirez.programming.kicks-ass.net
[ Drop the balance_push() hunk as it is not needed. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 72d0ad7cb5bad265adb2014dbe46c4ccb11afaba ] The time remaining until expiry of the refresh_timer can be negative. Casting the type to an unsigned 64-bit value will cause integer underflow, making the runtime_refresh_within return false instead of true. These situations are rare, but they do happen. This does not cause user-facing issues or errors; other than possibly unthrottling cfs_rq's using runtime from the previous period(s), making the CFS bandwidth enforcement less strict in those (special) situations. Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ben Segall <bsegall@google.com> Link: https://lore.kernel.org/r/20210629121452.18429-1-odin@uged.al Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 1c35b07e6d3986474e5635be566e7bc79d97c64d ] The _sum and _avg values are in general sync together with the PELT divider. They are however not always completely in perfect sync, resulting in situations where _sum gets to zero while _avg stays positive. Such situations are undesirable. This comes from the fact that PELT will increase period_contrib, also increasing the PELT divider, without updating _sum and _avg values to stay in perfect sync where (_sum == _avg * divider). However, such PELT change will never lower _sum, making it impossible to end up in a situation where _sum is zero and _avg is not. Therefore, we need to ensure that when subtracting load outside PELT, that when _sum is zero, _avg is also set to zero. This occurs when (_sum < _avg * divider), and the subtracted (_avg * divider) is bigger or equal to the current _sum, while the subtracted _avg is smaller than the current _avg. Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Link: https://lore.kernel.org/r/20210624111815.57937-1-odin@uged.al Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 08f7c2f4d0e9f4283f5796b8168044c034a1bfcb ] When using something other than 8 spaces per tab, this ascii art makes not sense, and the reader might end up wondering what this advanced equation "is". Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lkml.kernel.org/r/20210518125202.78658-4-odin@uged.al Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit fcf6631f3736985ec89bdd76392d3c7bfb60119f ] Rounding in PELT calculation happening when entities are attached/detached of a cfs_rq can result into situations where util/runnable_avg is not null but util/runnable_sum is. This is normally not possible so we need to ensure that util/runnable_sum stays synced with util/runnable_avg. detach_entity_load_avg() is the last place where we don't sync util/runnable_sum with util/runnbale_avg when moving some sched_entities Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210601085832.12626-1-vincent.guittot@linaro.org Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 68d7a190682aa4eb02db477328088ebad15acc83 upstream.
The util_est internal UTIL_AVG_UNCHANGED flag which is used to prevent
unnecessary util_est updates uses the LSB of util_est.enqueued. It is
exposed via _task_util_est() (and task_util_est()).
Commit 92a801e5d5b7 ("sched/fair: Mask UTIL_AVG_UNCHANGED usages")
mentions that the LSB is lost for util_est resolution but
find_energy_efficient_cpu() checks if task_util_est() returns 0 to
return prev_cpu early.
_task_util_est() returns the max value of util_est.ewma and
util_est.enqueued or'ed w/ UTIL_AVG_UNCHANGED.
So task_util_est() returning the max of task_util() and
_task_util_est() will never return 0 under the default
SCHED_FEAT(UTIL_EST, true).
To fix this use the MSB of util_est.enqueued instead and keep the flag
util_est internal, i.e. don't export it via _task_util_est().
The maximal possible util_avg value for a task is 1024 so the MSB of
'unsigned int util_est.enqueued' isn't used to store a util value.
As a caveat the code behind the util_est_se trace point has to filter
UTIL_AVG_UNCHANGED to see the real util_est.enqueued value which should
be easy to do.
This also fixes an issue report by Xuewen Yan that util_est_update()
only used UTIL_AVG_UNCHANGED for the subtrahend of the equation:
last_enqueued_diff = ue.enqueued - (task_util() | UTIL_AVG_UNCHANGED)
Fixes: b89997aa88f0b sched/pelt: Fix task util_est update filtering
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Xuewen Yan <xuewen.yan@unisoc.com>
Reviewed-by: Vincent Donnefort <vincent.donnefort@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20210602145808.1562603-1-dietmar.eggemann@arm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 02da26ad5ed6ea8680e5d01f20661439611ed776 upstream.
During the update of fair blocked load (__update_blocked_fair()), we
update the contribution of the cfs in tg->load_avg if cfs_rq's pelt
has decayed. Nevertheless, the pelt values of a cfs_rq could have
been recently updated while propagating the change of a child. In this
case, cfs_rq's pelt will not decayed because it has already been
updated and we don't update tg->load_avg.
__update_blocked_fair
...
for_each_leaf_cfs_rq_safe: child cfs_rq
update cfs_rq_load_avg() for child cfs_rq
...
update_load_avg(cfs_rq_of(se), se, 0)
...
update cfs_rq_load_avg() for parent cfs_rq
-propagation of child's load makes parent cfs_rq->load_sum
becoming null
-UPDATE_TG is not set so it doesn't update parent
cfs_rq->tg_load_avg_contrib
..
for_each_leaf_cfs_rq_safe: parent cfs_rq
update cfs_rq_load_avg() for parent cfs_rq
- nothing to do because parent cfs_rq has already been updated
recently so cfs_rq->tg_load_avg_contrib is not updated
...
parent cfs_rq is decayed
list_del_leaf_cfs_rq parent cfs_rq
- but it still contibutes to tg->load_avg
we must set UPDATE_TG flags when propagting pending load to the parent
Fixes: 039ae8bcf7a5 ("sched/fair: Fix O(nr_cgroups) in the load balancing path")
Reported-by: Odin Ugedal <odin@uged.al>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Odin Ugedal <odin@uged.al>
Link: https://lkml.kernel.org/r/20210527122916.27683-3-vincent.guittot@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 7c7ad626d9a0ff0a36c1e2a3cfbbc6a13828d5eb upstream.
when removing a cfs_rq from the list we only check _sum value so we must
ensure that _avg and _sum stay synced so load_sum can't be null whereas
load_avg is not after propagating load in the cgroup hierarchy.
Use load_avg to compute load_sum similarly to what is done for util_sum
and runnable_sum.
Fixes: 0e2d2aaaae52 ("sched/fair: Rewrite PELT migration propagation")
Reported-by: Odin Ugedal <odin@uged.al>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Odin Ugedal <odin@uged.al>
Link: https://lkml.kernel.org/r/20210527122916.27683-2-vincent.guittot@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 0258bdfaff5bd13c4d2383150b7097aecd6b6d82 ]
This fixes an issue where old load on a cfs_rq is not properly decayed,
resulting in strange behavior where fairness can decrease drastically.
Real workloads with equally weighted control groups have ended up
getting a respective 99% and 1%(!!) of cpu time.
When an idle task is attached to a cfs_rq by attaching a pid to a cgroup,
the old load of the task is attached to the new cfs_rq and sched_entity by
attach_entity_cfs_rq. If the task is then moved to another cpu (and
therefore cfs_rq) before being enqueued/woken up, the load will be moved
to cfs_rq->removed from the sched_entity. Such a move will happen when
enforcing a cpuset on the task (eg. via a cgroup) that force it to move.
The load will however not be removed from the task_group itself, making
it look like there is a constant load on that cfs_rq. This causes the
vruntime of tasks on other sibling cfs_rq's to increase faster than they
are supposed to; causing severe fairness issues. If no other task is
started on the given cfs_rq, and due to the cpuset it would not happen,
this load would never be properly unloaded. With this patch the load
will be properly removed inside update_blocked_averages. This also
applies to tasks moved to the fair scheduling class and moved to another
cpu, and this path will also fix that. For fork, the entity is queued
right away, so this problem does not affect that.
This applies to cases where the new process is the first in the cfs_rq,
issue introduced 3d30544f0212 ("sched/fair: Apply more PELT fixes"), and
when there has previously been load on the cgroup but the cgroup was
removed from the leaflist due to having null PELT load, indroduced
in 039ae8bcf7a5 ("sched/fair: Fix O(nr_cgroups) in the load balancing
path").
For a simple cgroup hierarchy (as seen below) with two equally weighted
groups, that in theory should get 50/50 of cpu time each, it often leads
to a load of 60/40 or 70/30.
parent/
cg-1/
cpu.weight: 100
cpuset.cpus: 1
cg-2/
cpu.weight: 100
cpuset.cpus: 1
If the hierarchy is deeper (as seen below), while keeping cg-1 and cg-2
equally weighted, they should still get a 50/50 balance of cpu time.
This however sometimes results in a balance of 10/90 or 1/99(!!) between
the task groups.
$ ps u -C stress
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 18568 1.1 0.0 3684 100 pts/12 R+ 13:36 0:00 stress --cpu 1
root 18580 99.3 0.0 3684 100 pts/12 R+ 13:36 0:09 stress --cpu 1
parent/
cg-1/
cpu.weight: 100
sub-group/
cpu.weight: 1
cpuset.cpus: 1
cg-2/
cpu.weight: 100
sub-group/
cpu.weight: 10000
cpuset.cpus: 1
This can be reproduced by attaching an idle process to a cgroup and
moving it to a given cpuset before it wakes up. The issue is evident in
many (if not most) container runtimes, and has been reproduced
with both crun and runc (and therefore docker and all its "derivatives"),
and with both cgroup v1 and v2.
Fixes: 3d30544f0212 ("sched/fair: Apply more PELT fixes")
Fixes: 039ae8bcf7a5 ("sched/fair: Fix O(nr_cgroups) in the load balancing path")
Signed-off-by: Odin Ugedal <odin@uged.al>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210501141950.23622-2-odin@uged.al
Signed-off-by: Sasha Levin <sashal@kernel.org>