Commit dfda9718 authored Oct 28, 2017 by Chris Redpath Committed by Gerrit - the friendly Code Review server May 13, 2019

ANDROID: sched/fair: Reduce balance interval to 1 jiffy if we have a misfit task



It is quite a common occurrence that we have a misfit task (a task
running on a CPU which is close to the capacity limit of that CPU)
in the system AND we have recently done a load balance operation.
Normal load-balance rate limiting means we can leave those tasks on
the restrictive CPU for a few hundred ms before we move them.

Inspired by the work Leo Yan did on balancing misfits.

This patch reduces the balance interval to one jiffy when there are such
tasks running.

There appears to be no impact on interactive performance from this
patch.

Change-Id: I71d74734d3bd6bca80476c0f466ba48914b7ac02
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
Git-commit: 84c88fc37932db51b87af8df3cedc621cb5c6e97
Git-repo: https://android.googlesource.com/kernel/common


[clingutla@codeaurora.org: Took only partial part from commit
  '84c88fc37932("ANDROID: Combined EAS Load Balance Tweaks")',
  and skip using 1 jiffy for busy balancing]
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>

parent f836be56

kernel/sched/fair.c

+19 −0

Original line number	Diff line number	Diff line
		@@ -10566,6 +10566,7 @@ static inline unsigned long
		get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
		{
		unsigned long interval = sd->balance_interval;
		unsigned int cpu;

		if (cpu_busy)
		interval *= sd->busy_factor;
		@@ -10574,6 +10575,24 @@ get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
		interval = msecs_to_jiffies(interval);
		interval = clamp(interval, 1UL, max_load_balance_interval);

		/*
		* check if sched domain is marked as overutilized
		* we ought to only do this on systems which have SD_ASYMCAPACITY
		* but we want to do it for all sched domains in those systems
		* So for now, just check if overutilized as a proxy.
		*/
		/*
		* If we are overutilized and we have a misfit task, then
		* we want to balance as soon as practically possible, so
		* we return an interval of zero, except for busy balance.
		*/
		if (sd_overutilized(sd) && !cpu_busy) {
		/* we know the root is overutilized, let's check for a misfit task */
		for_each_cpu(cpu, sched_domain_span(sd)) {
		if (cpu_rq(cpu)->misfit_task_load)
		return 1;
		}
		}
		return interval;
		}