From: Mel Gorman <mgorman@suse.de>
To: Barry Song <song.bao.hua@hisilicon.com>
Cc: vincent.guittot@linaro.org, mingo@redhat.com,
peterz@infradead.org, juri.lelli@redhat.com,
dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, valentin.schneider@arm.com,
aubrey.li@linux.intel.com, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, xuwei5@huawei.com,
prime.zeng@hisilicon.com, guodong.xu@linaro.org,
yangyicong@huawei.com, liguozhu@hisilicon.com,
linuxarm@openeuler.org
Subject: Re: [PATCH] sched/fair: remove redundant test_idle_cores for non-smt
Date: Mon, 22 Mar 2021 10:15:57 +0000 [thread overview]
Message-ID: <20210322101556.GK15768@suse.de> (raw)
In-Reply-To: <20210320221432.924-1-song.bao.hua@hisilicon.com>
On Sun, Mar 21, 2021 at 11:14:32AM +1300, Barry Song wrote:
> 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 could 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 non-smt machines.
>
> we run the below hackbench with different -g parameter from 2 to
> 14, for each different g, we run the command 10 times and get the
> average time:
> $ numactl -N 0 hackbench -p -T -l 20000 -g $1
>
> hackbench will report the time which is needed to complete a certain
> number of messages transmissions between a certain number of tasks,
> for example:
> $ numactl -N 0 hackbench -p -T -l 20000 -g 10
> Running in threaded mode with 10 groups using 40 file descriptors each
> (== 400 tasks)
> Each sender will pass 20000 messages of 100 bytes
>
> 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>
Acked-by: Mel Gorman <mgorman@suse.de>
That said, the numa_idle_core() function then becomes slightly
redundant. A possible follow up is to move the "idle_core >= 0" check
in numa_idle_core() to its caller in update_numa_stats() and then remove
the redundant check in !static_branch_likely(&sched_smt_present) check
in numa_idle_core.
--
Mel Gorman
SUSE Labs
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next prev parent reply other threads:[~2021-03-22 10:18 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-20 22:14 [PATCH] sched/fair: remove redundant test_idle_cores for non-smt Barry Song
2021-03-22 4:36 ` Li, Aubrey
2021-03-22 5:08 ` [Linuxarm] " Song Bao Hua (Barry Song)
2021-03-22 10:15 ` Mel Gorman [this message]
2021-03-22 11:09 ` Peter Zijlstra
2021-03-22 13:11 ` Vincent Guittot
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