linux-kernel - Re: [PATCH 02/14] perf/bench: Default to all routines in 'perf bench mem'

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Message-ID: <CA+55aFzAZwC69kZg3W8Mp6ERQOXXY3=U7jKpWqxDWi6W=6Z12Q@mail.gmail.com>
Date:	Mon, 19 Oct 2015 08:21:35 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...hat.com>,
	Hitoshi Mitake <mitake@....info.waseda.ac.jp>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 02/14] perf/bench: Default to all routines in 'perf bench mem'

On Mon, Oct 19, 2015 at 1:04 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
>         triton:~> perf bench mem all
>         # Running mem/memcpy benchmark...
>         Routine default (Default memcpy() provided by glibc)
>                4.957170 GB/Sec (with prefault)
>         Routine x86-64-unrolled (unrolled memcpy() in arch/x86/lib/memcpy_64.S)
>                4.379204 GB/Sec (with prefault)
>         Routine x86-64-movsq (movsq-based memcpy() in arch/x86/lib/memcpy_64.S)
>                4.264465 GB/Sec (with prefault)
>         Routine x86-64-movsb (movsb-based memcpy() in arch/x86/lib/memcpy_64.S)
>                6.554111 GB/Sec (with prefault)

Is this skylake? And why are the numbers so low? Even on my laptop
(Haswell), I get ~21GB/s (when setting cpufreq to performance).

It's interesting that 'movsb' for you is so much better. It's been
promising before, and it *should* be able to do better than manual
copying, but it's not been that noticeable on the machines I've
tested. But I haven't ued Skylake or Broadwell yet.

cpufreq might be making a difference too. Maybe it's just ramping up
the CPU? Or is that really repeatable?

                     Linus
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