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linux-next/kernel/sched
Vincent Guittot 01cfcde9c2 sched/fair: handle case of task_h_load() returning 0
task_h_load() can return 0 in some situations like running stress-ng
mmapfork, which forks thousands of threads, in a sched group on a 224 cores
system. The load balance doesn't handle this correctly because
env->imbalance never decreases and it will stop pulling tasks only after
reaching loop_max, which can be equal to the number of running tasks of
the cfs. Make sure that imbalance will be decreased by at least 1.

misfit task is the other feature that doesn't handle correctly such
situation although it's probably more difficult to face the problem
because of the smaller number of CPUs and running tasks on heterogenous
system.

We can't simply ensure that task_h_load() returns at least one because it
would imply to handle underflow in other places.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: <stable@vger.kernel.org> # v4.4+
Link: https://lkml.kernel.org/r/20200710152426.16981-1-vincent.guittot@linaro.org
2020-07-16 23:19:48 +02:00
..
autogroup.c sched/autogroup: Make autogroup_path() always available 2019-06-24 19:23:40 +02:00
autogroup.h sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
clock.c sched/clock: Use static_branch_likely() with sched_clock_running 2019-11-29 08:10:54 +01:00
completion.c completion: Use lockdep_assert_RT_in_threaded_ctx() in complete_all() 2020-03-23 18:40:25 +01:00
core.c sched: Fix unreliable rseq cpu_id for new tasks 2020-07-08 11:38:50 +02:00
cpuacct.c sched/cpuacct: Fix charge cpuacct.usage_sys 2020-05-19 20:34:14 +02:00
cpudeadline.c Linux 5.2-rc5 2019-06-17 12:12:27 +02:00
cpudeadline.h sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
cpufreq_schedutil.c sched/uclamp: Rename uclamp_util_with() into uclamp_rq_util_with() 2019-12-25 10:42:08 +01:00
cpufreq.c cpufreq: Avoid leaving stale IRQ work items during CPU offline 2019-12-12 17:59:43 +01:00
cpupri.c sched/rt: cpupri_find: Trigger a full search as fallback 2020-03-20 13:06:20 +01:00
cpupri.h sched/rt: Optimize cpupri_find() on non-heterogenous systems 2020-03-06 12:57:27 +01:00
cputime.c sched/vtime: Work around an unitialized variable warning 2020-04-15 11:06:50 +02:00
deadline.c sched/deadline: Initialize ->dl_boosted 2020-06-28 17:01:20 +02:00
debug.c sched: Add rq::ttwu_pending 2020-05-28 10:54:16 +02:00
fair.c sched/fair: handle case of task_h_load() returning 0 2020-07-16 23:19:48 +02:00
features.h sched/fair/util_est: Implement faster ramp-up EWMA on utilization increases 2019-10-29 10:01:07 +01:00
idle.c cpuidle: Rearrange s2idle-specific idle state entry code 2020-06-25 13:52:53 +02:00
isolation.c sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters 2020-04-15 10:38:26 +02:00
loadavg.c timers/nohz: Update NOHZ load in remote tick 2020-01-28 21:36:44 +01:00
Makefile kcsan: Improve various small stylistic details 2019-11-20 10:47:23 +01:00
membarrier.c membarrier: Fix RCU locking bug caused by faulty merge 2019-10-01 21:27:50 +02:00
pelt.c sched/pelt: Sync util/runnable_sum with PELT window when propagating 2020-05-19 20:34:14 +02:00
pelt.h sched/pelt: Add support to track thermal pressure 2020-03-06 12:57:17 +01:00
psi.c psi: Move PF_MEMSTALL out of task->flags 2020-03-20 13:06:19 +01:00
rt.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-06-03 16:27:18 -07:00
sched-pelt.h sched/fair: Fix "runnable_avg_yN_inv" not used warnings 2019-06-17 12:15:58 +02:00
sched.h sched/core: s/WF_ON_RQ/WQ_ON_CPU/ 2020-06-28 17:01:20 +02:00
smp.h sched/headers: Split out open-coded prototypes into kernel/sched/smp.h 2020-05-28 11:03:20 +02:00
stats.c proc: introduce proc_create_seq{,_data} 2018-05-16 07:23:35 +02:00
stats.h psi: Move PF_MEMSTALL out of task->flags 2020-03-20 13:06:19 +01:00
stop_task.c sched/core: Further clarify sched_class::set_next_task() 2019-11-11 08:35:21 +01:00
swait.c sched/swait: Prepare usage in completions 2020-03-21 16:00:23 +01:00
topology.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-06-03 16:27:18 -07:00
wait_bit.c sched/wait: fix ___wait_var_event(exclusive) 2019-12-17 13:32:50 +01:00
wait.c Add wake_up_interruptible_sync_poll_locked() 2019-10-31 15:12:23 +00:00