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From: "David Wang" <00107082@163.com>
To: musl@lists.openwall.com
Cc: "Markus Wichmann" <nullplan@gmx.net>
Subject: [musl] Re:Re: [musl] Re:Re: [musl] Re:Re: [musl] qsort
Date: Fri, 10 Feb 2023 21:45:12 +0800 (CST)	[thread overview]
Message-ID: <23b37232.4d4c.1863b92aa13.Coremail.00107082@163.com> (raw)
In-Reply-To: <20230210131044.GZ4163@brightrain.aerifal.cx>




At 2023-02-10 21:10:45, "Rich Felker" <dalias@libc.org> wrote:
>On Fri, Feb 10, 2023 at 06:00:27PM +0800, David Wang wrote:

>What tool was used for this? gprof or anything else invasive is not
>meaningful; for tiny functions, the entire time measured will be the
>profiling overhead. perf(1) is the only way I know to get meaningful
>numbers.
>
>In particular, it makes no sense that significant time was spent in
>wrapper_cmp, which looks like (i386):
>
>   0:   ff 64 24 0c             jmp    *0xc(%esp)
>
>or (x86_64):
>
>   0:   ff e2                   jmpq   *%rdx
>
>or (arm):
>
>   0:   4710            bx      r2
>
>but I can imagine it being (relatively) gigantic with a call out to
>profiling code.
>
>Rich

I have myself implemented a profiling tool, using perf_event_open to start profiling and mmap to collect callchains, the source code is here  https://github.com/zq-david-wang/linux-tools/blob/main/perf/profiler/profiler.cpp
(Still buggy, there is always strange callchain which I could not figure out...and I am still working on it...) 

Also, I did not use any optimization when compile the code, which could make a difference, I will take time to give it a try .

About wrapper_cmp, in my last profiling, there are total  931387 samples collected, 257403 samples contain callchain  ->wrapper_cmp, among those 257403 samples,  167410 samples contain callchain ->wrapper_cmp->mycmp, 
that is why I think there is extra overhead about wrapper_cmp.   Maybe compiler optimization would change the result, and I will make further checks.


David




  reply	other threads:[~2023-02-10 13:45 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-20  1:49 Guy
2023-01-20 12:55 ` alice
2023-01-30 10:04   ` [musl] " David Wang
2023-02-01 18:01     ` Markus Wichmann
2023-02-02  2:12       ` [musl] " David Wang
2023-02-03  5:22         ` [musl] " David Wang
2023-02-03  8:03           ` Alexander Monakov
2023-02-03  9:01             ` [musl] " David Wang
2023-02-09 19:03       ` Rich Felker
2023-02-09 19:20         ` Alexander Monakov
2023-02-09 19:52           ` Rich Felker
2023-02-09 20:18             ` Rich Felker
2023-02-09 20:27               ` Pierpaolo Bernardi
2023-02-10  4:10             ` Markus Wichmann
2023-02-10 10:00         ` [musl] " David Wang
2023-02-10 13:10           ` Rich Felker
2023-02-10 13:45             ` David Wang [this message]
2023-02-10 14:19               ` [musl] " Rich Felker
2023-02-11  5:12                 ` [musl] " David Wang
2023-02-11  5:44                   ` alice
2023-02-11  8:39                     ` Joakim Sindholt
2023-02-11  9:06                       ` alice
2023-02-11  9:31                         ` [musl] " David Wang
2023-02-11 13:35                         ` Rich Felker
2023-02-11 17:18                           ` David Wang
2023-02-16 15:15       ` David Wang
2023-02-16 16:07         ` Rich Felker
2023-02-17  1:35           ` [musl] " David Wang
2023-02-17 13:17           ` Alexander Monakov
2023-02-17 15:07             ` Rich Felker
2023-02-11  9:22     ` [musl] " Markus Wichmann
2023-02-11  9:36       ` [musl] " David Wang
2023-02-11  9:51       ` David Wang
2023-01-20 13:32 ` [musl] qsort Valery Ushakov

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