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acb4decc1e
A long-tail load balance cost is observed on the newly idle path, this is caused by a race window between the first nr_running check of the busiest runqueue and its nr_running recheck in detach_tasks. Before the busiest runqueue is locked, the tasks on the busiest runqueue could be pulled by other CPUs and nr_running of the busiest runqueu becomes 1 or even 0 if the running task becomes idle, this causes detach_tasks breaks with LBF_ALL_PINNED flag set, and triggers load_balance redo at the same sched_domain level. In order to find the new busiest sched_group and CPU, load balance will recompute and update the various load statistics, which eventually leads to the long-tail load balance cost. This patch clears LBF_ALL_PINNED flag for this race condition, and hence reduces the long-tail cost of newly idle balance. Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lkml.kernel.org/r/1614154549-116078-1-git-send-email-aubrey.li@intel.com |
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| .. | ||
| autogroup.c | ||
| autogroup.h | ||
| clock.c | ||
| completion.c | ||
| core.c | ||
| cpuacct.c | ||
| cpudeadline.c | ||
| cpudeadline.h | ||
| cpufreq.c | ||
| cpufreq_schedutil.c | ||
| cpupri.c | ||
| cpupri.h | ||
| cputime.c | ||
| deadline.c | ||
| debug.c | ||
| fair.c | ||
| features.h | ||
| idle.c | ||
| isolation.c | ||
| loadavg.c | ||
| Makefile | ||
| membarrier.c | ||
| pelt.c | ||
| pelt.h | ||
| psi.c | ||
| rt.c | ||
| sched-pelt.h | ||
| sched.h | ||
| smp.h | ||
| stats.c | ||
| stats.h | ||
| stop_task.c | ||
| swait.c | ||
| topology.c | ||
| wait.c | ||
| wait_bit.c | ||