From: Barry Song <song.bao.hua@hisilicon.com> To: <vincent.guittot@linaro.org>, <mingo@redhat.com>, <peterz@infradead.org>, <juri.lelli@redhat.com>, <dietmar.eggemann@arm.com>, <rostedt@goodmis.org>, <bsegall@google.com>, <mgorman@suse.de> Cc: <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>, Barry Song <song.bao.hua@hisilicon.com> Subject: [PATCH] sched/fair: remove redundant test_idle_cores for non-smt Date: Sun, 21 Mar 2021 11:14:32 +1300 [thread overview] Message-ID: <20210320221432.924-1-song.bao.hua@hisilicon.com> (raw) 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> --- kernel/sched/fair.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2e2ab1e..de42a32 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6038,9 +6038,11 @@ 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; } -- 1.8.3.1
WARNING: multiple messages have this Message-ID (diff)
From: Barry Song <song.bao.hua@hisilicon.com> To: <vincent.guittot@linaro.org>, <mingo@redhat.com>, <peterz@infradead.org>, <juri.lelli@redhat.com>, <dietmar.eggemann@arm.com>, <rostedt@goodmis.org>, <bsegall@google.com>, <mgorman@suse.de> Cc: <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>, Barry Song <song.bao.hua@hisilicon.com> Subject: [PATCH] sched/fair: remove redundant test_idle_cores for non-smt Date: Sun, 21 Mar 2021 11:14:32 +1300 [thread overview] Message-ID: <20210320221432.924-1-song.bao.hua@hisilicon.com> (raw) 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> --- kernel/sched/fair.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2e2ab1e..de42a32 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6038,9 +6038,11 @@ 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; } -- 1.8.3.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2021-03-20 22:24 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-03-20 22:14 Barry Song [this message] 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 4:36 ` Li, Aubrey 2021-03-22 5:08 ` [Linuxarm] " Song Bao Hua (Barry Song) 2021-03-22 5:08 ` Song Bao Hua (Barry Song) 2021-03-22 10:15 ` Mel Gorman 2021-03-22 10:15 ` Mel Gorman 2021-03-22 11:09 ` Peter Zijlstra 2021-03-22 11:09 ` Peter Zijlstra 2021-03-22 13:11 ` Vincent Guittot 2021-03-22 13:11 ` Vincent Guittot 2021-03-23 15:08 ` [tip: sched/core] sched/fair: Optimize test_idle_cores() for !SMT tip-bot2 for Barry Song
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