Commit 33eabee8 authored Mar 22, 2016 by Pavankumar Kondeti

sched: qhmp: fix hmp_capable detection bug in small task CPU selection



The cpumask_full() returns true only if NR_CPUS bits are set in the
in the bitmask. If NR_CPUS is defined to a value greater than the
number of possible CPUs, hmp_capable returns true even for a SMP
system.

If hmp_capable returns true, the higher capacity cluster CPUs (i.e
all CPUs in a SMP system) are cleared from the initial search for
a mostly_idle CPU. As this search is not successful, the least
busy CPU including an idle CPU is returned while a mostly_idle CPU
is available.  This is resulting in power regression. Fix the
hmp_capable detection by comparing the mpc_mask and cpu_possible_mask
directly.

CRs-Fixed: 993166
Change-Id: Ic046ea300b3fe118df6bd98e54d088979fd90931
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>

parent 80f8814a

kernel/sched/qhmp_fair.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -3038,13 +3038,11 @@ static int best_small_task_cpu(struct task_struct *p, int sync)
		int i = task_cpu(p), prev_cpu;
		int hmp_capable;
		u64 tload, cpu_load, min_load = ULLONG_MAX;
		cpumask_t temp;
		cpumask_t search_cpu;
		cpumask_t fb_search_cpu = CPU_MASK_NONE;
		struct rq *rq;

		cpumask_and(&temp, &mpc_mask, cpu_possible_mask);
		hmp_capable = !cpumask_full(&temp);
		hmp_capable = !cpumask_equal(&mpc_mask, cpu_possible_mask);

		cpumask_and(&search_cpu, tsk_cpus_allowed(p), cpu_online_mask);
		if (unlikely(!cpumask_test_cpu(i, &search_cpu))) {