linux-kernel - Re: [PATCHSET 0/9] perf: Improve cgroup profiling (v3)

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Date:   Fri, 27 Dec 2019 13:31:29 -0500 (EST)
From:   Vince Weaver <vincent.weaver@...ne.edu>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
cc:     Namhyung Kim <namhyung@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Jiri Olsa <jolsa@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Stephane Eranian <eranian@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Adrian Hunter <adrian.hunter@...el.com>, mtk.manpages@...il.com
Subject: Re: [PATCHSET 0/9] perf: Improve cgroup profiling (v3)

On Thu, 26 Dec 2019, Arnaldo Carvalho de Melo wrote:

> Em Tue, Dec 24, 2019 at 09:40:04AM +0900, Namhyung Kim escreveu:
> > On Tue, Dec 24, 2019 at 2:35 AM Vince Weaver <vincent.weaver@...ne.edu> wrote:
> > > On Mon, 23 Dec 2019, Namhyung Kim wrote:
> > > > This work is to improve cgroup profiling in perf.  Currently it only
> > > > supports profiling tasks in a specific cgroup and there's no way to
> > > > identify which cgroup the current sample belongs to.  So I added
> > > > PERF_SAMPLE_CGROUP to add cgroup id into each sample.  It's a 64-bit
> > > > integer having file handle of the cgroup.  And kernel also generates
> > > > PERF_RECORD_CGROUP event for new groups to correlate the cgroup id and
> > > > cgroup name (path in the cgroup filesystem).  The cgroup id can be
> > > > read from userspace by name_to_handle_at() system call so it can
> > > > synthesize the CGROUP event for existing groups.
> 
> > > so is there a patch to the manpage that describes this new behavior in
> > > perf_event_open()?
> 
> > Not yet.  I'll cook a patch once it's merged to the Linus' tree.
> 
> Vince, was it ever considered to carry the man page in the kernel
> sources and then make it so that new features need to come with the
> respective changes to the man page? I think that would be a good move,
> you would be the maintainer for that file, what do you think?

While I do a lot of work on the perf_event_open() manpage,  it's part of 
the linux man-pages project so I don't really control where it is 
maintained.

I personally do not think it would help much merging into the kernel tree.
I still think the idea of moving everything into linux-git (such as the  
"perf" tool) isn't always the best idea and can make it harder for people
who aren't kernel developers to work on things.

Vince