https://github.com/torvalds/linux
Revision 01cfcde9c26d8555f0e6e9aea9d6049f87683998 authored by Vincent Guittot on 10 July 2020, 15:24:26 UTC, committed by Peter Zijlstra on 16 July 2020, 21:19:48 UTC
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
1 parent ce3614d
Tip revision: 01cfcde9c26d8555f0e6e9aea9d6049f87683998 authored by Vincent Guittot on 10 July 2020, 15:24:26 UTC
sched/fair: handle case of task_h_load() returning 0
sched/fair: handle case of task_h_load() returning 0
Tip revision: 01cfcde
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