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sched/fair: Optimize test_idle_cores() for !SMT

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update_idle_core() is only done for the case of sched_smt_present.
but test_idle_cores() is done for all machines even those without
SMT.

This can contribute to up 8%+ hackbench performance loss on a
machine like kunpeng 920 which has no SMT. This patch removes the
redundant test_idle_cores() for !SMT machines.

Hackbench is ran with -g {2..14}, for each g it is ran 10 times to get
an average.

  $ numactl -N 0 hackbench -p -T -l 20000 -g $1

The below is the result of hackbench w/ and w/o this patch:

  g=    2      4     6       8      10     12      14
  w/o: 1.8151 3.8499 5.5142 7.2491 9.0340 10.7345 12.0929
  w/ : 1.8428 3.7436 5.4501 6.9522 8.2882  9.9535 11.3367
			    +4.1%  +8.3%  +7.3%   +6.3%

Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Change-Id: I0dd9363d2b8da9dda0bed205a5ddc36f75fabeef
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Tashfin Shakeer Rhythm <tashfinshakeerrhythm@gmail.com>
(cherry picked from commit 7c201829c9c1e1ebb1384de66e02b8249d83167e)
Signed-off-by: TogoFire <togofire@mailfence.com>
Signed-off-by: onettboots <blackcocopet@gmail.com>
This commit is contained in:
Barry Song 2021-05-22 18:36:08 +08:00 committed by Ksawlii
parent 6b31cca191
commit b949395346
1 changed files with 5 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
kernel/sched/fair.c
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@ -6269,9 +6269,11 @@ static inline bool test_idle_cores(int cpu, bool def)
{
struct sched_domain_shared *sds;
sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
if (sds)
return READ_ONCE(sds->has_idle_cores);
if (static_branch_likely(&sched_smt_present)) {
sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
if (sds)
return READ_ONCE(sds->has_idle_cores);
}
return def;
}