linux/kernel/sched
Keisuke Nishimura 6d7e4782bc sched/fair: Fix the decision for load balance
should_we_balance is called for the decision to do load-balancing.
When sched ticks invoke this function, only one CPU should return
true. However, in the current code, two CPUs can return true. The
following situation, where b means busy and i means idle, is an
example, because CPU 0 and CPU 2 return true.

        [0, 1] [2, 3]
         b  b   i  b

This fix checks if there exists an idle CPU with busy sibling(s)
after looking for a CPU on an idle core. If some idle CPUs with busy
siblings are found, just the first one should do load-balancing.

Fixes: b1bfeab9b0 ("sched/fair: Consider the idle state of the whole core for load balance")
Signed-off-by: Keisuke Nishimura <keisuke.nishimura@inria.fr>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Chen Yu <yu.c.chen@intel.com>
Reviewed-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20231031133821.1570861-1-keisuke.nishimura@inria.fr
2023-11-14 22:27:01 +01:00
..
Makefile
autogroup.c
autogroup.h
build_policy.c
build_utility.c
clock.c
completion.c
core.c
core_sched.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
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