From: Ian Rogers <irogers@google.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
Andrii Nakryiko <andrii@kernel.org>,
linux-fsdevel@vger.kernel.org, brauner@kernel.org,
viro@zeniv.linux.org.uk, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
linux-mm@kvack.org, Arnaldo Carvalho de Melo <acme@kernel.org>,
"linux-perf-use." <linux-perf-users@vger.kernel.org>
Subject: Re: [PATCH 5/5] selftests/bpf: a simple benchmark tool for /proc/<pid>/maps APIs
Date: Sat, 4 May 2024 22:09:39 -0700 [thread overview]
Message-ID: <CAP-5=fWPig8-CLLBJ_rb3D6eNAKVY7KX_n_HcpGqL7gfe-=XXg@mail.gmail.com> (raw)
In-Reply-To: <CAEf4BzaUgGJVqw_yWOXASHManHQWGQV905Bd-wiaHj-mRob9gw@mail.gmail.com>
On Sat, May 4, 2024 at 2:57 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Sat, May 4, 2024 at 8:29 AM Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Fri, May 03, 2024 at 05:30:06PM -0700, Andrii Nakryiko wrote:
> > > Implement a simple tool/benchmark for comparing address "resolution"
> > > logic based on textual /proc/<pid>/maps interface and new binary
> > > ioctl-based PROCFS_PROCMAP_QUERY command.
> >
> > Of course an artificial benchmark of "read a whole file" vs. "a tiny
> > ioctl" is going to be different, but step back and show how this is
> > going to be used in the real world overall. Pounding on this file is
> > not a normal operation, right?
> >
>
> It's not artificial at all. It's *exactly* what, say, blazesym library
> is doing (see [0], it's Rust and part of the overall library API, I
> think C code in this patch is way easier to follow for someone not
> familiar with implementation of blazesym, but both implementations are
> doing exactly the same sequence of steps). You can do it even less
> efficiently by parsing the whole file, building an in-memory lookup
> table, then looking up addresses one by one. But that's even slower
> and more memory-hungry. So I didn't even bother implementing that, it
> would put /proc/<pid>/maps at even more disadvantage.
>
> Other applications that deal with stack traces (including perf) would
> be doing one of those two approaches, depending on circumstances and
> level of sophistication of code (and sensitivity to performance).
The code in perf doing this is here:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/util/synthetic-events.c#n440
The code is using the api/io.h code:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/lib/api/io.h
Using perf to profile perf it was observed time was spent allocating
buffers and locale related activities when using stdio, so io is a
lighter weight alternative, albeit with more verbose code than fscanf.
You could add this as an alternate /proc/<pid>/maps reader, we have a
similar benchmark in `perf bench internals synthesize`.
Thanks,
Ian
> [0] https://github.com/libbpf/blazesym/blob/ee9b48a80c0b4499118a1e8e5d901cddb2b33ab1/src/normalize/user.rs#L193
>
> > thanks,
> >
> > greg k-h
>
next prev parent reply other threads:[~2024-05-05 5:09 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-04 0:30 [PATCH 0/5] ioctl()-based API to query VMAs from /proc/<pid>/maps Andrii Nakryiko
2024-05-04 0:30 ` [PATCH 1/5] fs/procfs: extract logic for getting VMA name constituents Andrii Nakryiko
2024-05-04 0:30 ` [PATCH 2/5] fs/procfs: implement efficient VMA querying API for /proc/<pid>/maps Andrii Nakryiko
2024-05-04 15:28 ` Greg KH
2024-05-04 21:50 ` Andrii Nakryiko
2024-05-06 13:58 ` Arnaldo Carvalho de Melo
2024-05-06 18:05 ` Namhyung Kim
2024-05-06 18:51 ` Andrii Nakryiko
2024-05-06 18:53 ` Arnaldo Carvalho de Melo
2024-05-06 19:16 ` Arnaldo Carvalho de Melo
2024-05-07 21:55 ` Namhyung Kim
2024-05-06 18:41 ` Andrii Nakryiko
2024-05-06 20:35 ` Arnaldo Carvalho de Melo
2024-05-07 16:36 ` Andrii Nakryiko
2024-05-04 23:36 ` kernel test robot
2024-05-07 18:10 ` Liam R. Howlett
2024-05-07 18:52 ` Andrii Nakryiko
2024-05-04 0:30 ` [PATCH 3/5] tools: sync uapi/linux/fs.h header into tools subdir Andrii Nakryiko
2024-05-04 0:30 ` [PATCH 4/5] selftests/bpf: make use of PROCFS_PROCMAP_QUERY ioctl, if available Andrii Nakryiko
2024-05-04 0:30 ` [PATCH 5/5] selftests/bpf: a simple benchmark tool for /proc/<pid>/maps APIs Andrii Nakryiko
2024-05-04 15:29 ` Greg KH
2024-05-04 21:57 ` Andrii Nakryiko
2024-05-05 5:09 ` Ian Rogers [this message]
2024-05-06 18:32 ` Andrii Nakryiko
2024-05-06 18:43 ` Ian Rogers
2024-05-07 5:06 ` Andrii Nakryiko
2024-05-07 17:29 ` Andrii Nakryiko
2024-05-07 22:27 ` Namhyung Kim
2024-05-07 22:56 ` Andrii Nakryiko
2024-05-08 0:36 ` Arnaldo Carvalho de Melo
2024-05-04 15:32 ` Greg KH
2024-05-04 22:13 ` Andrii Nakryiko
2024-05-07 15:48 ` Liam R. Howlett
2024-05-07 16:10 ` Matthew Wilcox
2024-05-07 16:18 ` Liam R. Howlett
2024-05-07 16:27 ` Andrii Nakryiko
2024-05-07 18:06 ` Liam R. Howlett
2024-05-07 19:00 ` Andrii Nakryiko
2024-05-08 1:20 ` Liam R. Howlett
2024-05-04 11:24 ` [PATCH 0/5] ioctl()-based API to query VMAs from /proc/<pid>/maps Christian Brauner
2024-05-04 15:33 ` Greg KH
2024-05-04 21:50 ` Andrii Nakryiko
2024-05-04 21:50 ` Andrii Nakryiko
2024-05-05 5:26 ` Ian Rogers
2024-05-06 18:58 ` Andrii Nakryiko
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