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authorPaul Turner <pjt@google.com>2020-03-10 18:01:13 -0700
committerPeter Zijlstra <peterz@infradead.org>2020-03-20 13:06:18 +0100
commit46a87b3851f0d6eb05e6d83d5c5a30df0eca8f76 (patch)
treeb98cf01a4a12e708f063c07788f7a3a7b41a93f2 /kernel/smpboot.c
parentfe61468b2cbc2b7ce5f8d3bf32ae5001d4c434e9 (diff)
sched/core: Distribute tasks within affinity masks
Currently, when updating the affinity of tasks via either cpusets.cpus, or, sched_setaffinity(); tasks not currently running within the newly specified mask will be arbitrarily assigned to the first CPU within the mask. This (particularly in the case that we are restricting masks) can result in many tasks being assigned to the first CPUs of their new masks. This: 1) Can induce scheduling delays while the load-balancer has a chance to spread them between their new CPUs. 2) Can antogonize a poor load-balancer behavior where it has a difficult time recognizing that a cross-socket imbalance has been forced by an affinity mask. This change adds a new cpumask interface to allow iterated calls to distribute within the intersection of the provided masks. The cases that this mainly affects are: - modifying cpuset.cpus - when tasks join a cpuset - when modifying a task's affinity via sched_setaffinity(2) Signed-off-by: Paul Turner <pjt@google.com> Signed-off-by: Josh Don <joshdon@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Qais Yousef <qais.yousef@arm.com> Tested-by: Qais Yousef <qais.yousef@arm.com> Link: https://lkml.kernel.org/r/20200311010113.136465-1-joshdon@google.com
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