From: Jiri Olsa <jolsa@redhat.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: acme@kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org,
eranian@google.com, kan.liang@linux.intel.com,
peterz@infradead.org
Subject: Re: Optimize perf stat for large number of events/cpus v2
Date: Tue, 22 Oct 2019 10:02:23 +0200 [thread overview]
Message-ID: <20191022080223.GC28177@krava> (raw)
In-Reply-To: <20191020175202.32456-1-andi@firstfloor.org>
On Sun, Oct 20, 2019 at 10:51:53AM -0700, Andi Kleen wrote:
> [The earlier v1 version had a lot of conflicts against some
> recent libperf changes in tip/perf/core. Resolve that and
> also fix some minor issues.]
>
> This patch kit optimizes perf stat for a large number of events
> on systems with many CPUs and PMUs.
>
> Some profiling shows that the most overhead is doing IPIs to
> all the target CPUs. We can optimize this by using sched_setaffinity
> to set the affinity to a target CPU once and then doing
> the perf operation for all events on that CPU. This requires
> some restructuring, but cuts the set up time quite a bit.
>
> In theory we could go further by parallelizing these setups
> too, but that would be much more complicated and for now just batching it
> per CPU seems to be sufficient. At some point with many more cores
> parallelization or a better bulk perf setup API might be needed though.
>
> In addition perf does a lot of redundant /sys accesses with
> many PMUs, which can be also expensve. This is also optimized.
>
> On a large test case (>700 events with many weak groups) on a 94 CPU
> system I go from
>
> real 0m8.607s
> user 0m0.550s
> sys 0m8.041s
>
> to
>
> real 0m3.269s
> user 0m0.760s
> sys 0m1.694s
>
> so shaving ~6 seconds of system time, at slightly more cost
> in perf stat itself. On a 4 socket system with the savings
> are more dramatic:
>
> real 0m15.641s
> user 0m0.873s
> sys 0m14.729s
>
> to
>
> real 0m4.493s
> user 0m1.578s
> sys 0m2.444s
>
> so 11s difference in the user visible set up time.
>
> Also available in
>
> git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc perf/stat-scale-4
>
> v1: Initial post.
> v2: Rebase. Fix some minor issues.
looks really helpful, I ack-ed 1st 2 patches,
I'll need more time for the rest
thanks,
jirka
next prev parent reply other threads:[~2019-10-22 8:02 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-20 17:51 Optimize perf stat for large number of events/cpus v2 Andi Kleen
2019-10-20 17:51 ` [PATCH v2 1/9] perf evsel: Always preserve errno while cleaning up perf_event_open failures Andi Kleen
2019-10-22 8:01 ` Jiri Olsa
2019-11-12 11:18 ` [tip: perf/core] " tip-bot2 for Andi Kleen
2019-10-20 17:51 ` [PATCH v2 2/9] perf evsel: Avoid close(-1) Andi Kleen
2019-10-22 8:01 ` Jiri Olsa
2019-11-12 11:18 ` [tip: perf/core] " tip-bot2 for Andi Kleen
2019-10-20 17:51 ` [PATCH v2 3/9] perf pmu: Use file system cache to optimize sysfs access Andi Kleen
2019-10-23 9:47 ` Jiri Olsa
2019-10-20 17:51 ` [PATCH v2 4/9] perf affinity: Add infrastructure to save/restore affinity Andi Kleen
2019-10-23 9:59 ` Jiri Olsa
2019-10-23 13:02 ` Andi Kleen
2019-10-23 14:30 ` Jiri Olsa
2019-10-23 14:52 ` Andi Kleen
2019-10-23 16:16 ` Alexey Budankov
2019-10-23 17:19 ` Andi Kleen
2019-10-23 18:08 ` Alexey Budankov
2019-10-23 22:37 ` Andi Kleen
2019-10-24 8:46 ` Alexey Budankov
2019-10-20 17:51 ` [PATCH v2 5/9] perf evsel: Add iterator to iterate over events ordered by CPU Andi Kleen
2019-10-20 17:51 ` [PATCH v2 6/9] perf stat: Use affinity for closing file descriptors Andi Kleen
2019-10-20 17:52 ` [PATCH v2 7/9] perf stat: Use affinity for opening events Andi Kleen
2019-10-20 17:52 ` [PATCH v2 8/9] perf stat: Use affinity for reading Andi Kleen
2019-10-20 17:52 ` [PATCH v2 9/9] perf stat: Use affinity for enabling/disabling events Andi Kleen
2019-10-23 10:30 ` Jiri Olsa
2019-10-23 13:07 ` Andi Kleen
2019-10-22 8:02 ` Jiri Olsa [this message]
2019-10-22 14:11 ` Optimize perf stat for large number of events/cpus v2 Arnaldo Carvalho de Melo
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