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From: Song Liu <liu.song.a23@gmail.com>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Tejun Heo <tj@kernel.org>, Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>, Jiri Olsa <jolsa@redhat.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Stephane Eranian <eranian@google.com>,
	Li Zefan <lizefan@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH 2/9] perf/core: Add PERF_SAMPLE_CGROUP feature
Date: Fri, 20 Sep 2019 09:13:04 -0700	[thread overview]
Message-ID: <CAPhsuW6zxkKd3ExXj5GCq+4yEWv85qmM9_Weatv4PoVd+aWKDQ@mail.gmail.com> (raw)
In-Reply-To: <CAM9d7cg_AKCyifV7xDm7sJ4=wgG_K=qu013TSTHqLiCRh9m_pg@mail.gmail.com>

Hi Namhyung,

On Fri, Sep 20, 2019 at 1:47 AM Namhyung Kim <namhyung@kernel.org> wrote:
>
> Hello Song,
>
> On Thu, Sep 19, 2019 at 3:43 PM Song Liu <liu.song.a23@gmail.com> wrote:
>
> > Sharing some offline discussions with Tejun.
> >
> > ino in current kernfs is not a good unique ID for cgroup, because it doesn't
> > increase monotonically. So we need to improve kernfs.
> >
> > For 64-bit, we can make the ino monotonic, and use it as the ID.
> > For 32-bit, we need to make the ino monotonic. and use <ino> and <gen>
> > as the 64-bit ID.
>
> Thanks for the sharing information!  For 32-bit, while the ino itself is not
> monotonic, gen << 32 + ino is monotonic right?  I think we can use the
> same logic of kernfs id allocation, but not sure what the problem Tejun
> mentioned before is.

How would we manage gen here? One way that works is:
1. make ino monotonic,
2. increase gen when 32-bit ino overflows

I think current kernfs id is not monotonic, so it can be reused before overflow.

Thanks,
Song

  reply	other threads:[~2019-09-20 16:13 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-28  7:31 [PATCHSET 0/9] perf: Improve cgroup profiling (v1) Namhyung Kim
2019-08-28  7:31 ` [PATCH 1/9] perf/core: Add PERF_RECORD_CGROUP event Namhyung Kim
2019-08-28  9:44   ` Peter Zijlstra
2019-08-28  9:44   ` Peter Zijlstra
2019-08-28 13:13     ` Arnaldo Carvalho de Melo
2019-08-30  3:46     ` Namhyung Kim
2019-08-30  7:34       ` Peter Zijlstra
2019-08-30 22:49         ` Namhyung Kim
2019-08-30 23:52           ` Stephane Eranian
2019-08-28 14:48   ` Tejun Heo
2019-08-30  3:56     ` Namhyung Kim
2019-08-28  7:31 ` [PATCH 2/9] perf/core: Add PERF_SAMPLE_CGROUP feature Namhyung Kim
2019-08-28 14:49   ` Tejun Heo
2019-08-31  3:03     ` Namhyung Kim
2019-08-31  4:58       ` Tejun Heo
2019-09-03  2:13         ` Namhyung Kim
2019-09-05 16:56           ` Tejun Heo
2019-09-08 13:28             ` Namhyung Kim
2019-09-14 14:02         ` Song Liu
2019-09-16 15:23           ` Tejun Heo
2019-09-19  6:42             ` Song Liu
2019-09-20  8:47               ` Namhyung Kim
2019-09-20 16:13                 ` Song Liu [this message]
2019-09-20 21:04                 ` Tejun Heo
2019-10-02  6:28                   ` Namhyung Kim
2019-10-07 14:16                     ` Tejun Heo
2019-08-28  7:31 ` [PATCH 3/9] perf tools: Basic support for CGROUP event Namhyung Kim
2019-08-30 12:55   ` Arnaldo Carvalho de Melo
2019-08-30 22:51     ` Namhyung Kim
2019-08-28  7:31 ` [PATCH 4/9] perf tools: Maintain cgroup hierarchy Namhyung Kim
2019-08-28  7:31 ` [PATCH 5/9] perf report: Add 'cgroup' sort key Namhyung Kim
2019-08-28  7:31 ` [PATCH 6/9] perf record: Support synthesizing cgroup events Namhyung Kim
2019-08-28  7:31 ` [PATCH 7/9] perf record: Add --all-cgroups option Namhyung Kim
2019-08-28  7:31 ` [PATCH 8/9] perf top: " Namhyung Kim
2019-08-28  7:31 ` [PATCH 9/9] perf script: Add --show-cgroup-events option Namhyung Kim
2019-12-20  4:32 [PATCHSET 0/9] perf: Improve cgroup profiling (v2) Namhyung Kim
2019-12-20  4:32 ` [PATCH 2/9] perf/core: Add PERF_SAMPLE_CGROUP feature Namhyung Kim
2019-12-20  9:36   ` Peter Zijlstra
2019-12-20 15:23   ` Tejun Heo
2019-12-20 16:48     ` Peter Zijlstra
2019-12-20 16:59       ` Tejun Heo
2019-12-23  6:07 [PATCHSET 0/9] perf: Improve cgroup profiling (v3) Namhyung Kim
2019-12-23  6:07 ` [PATCH 2/9] perf/core: Add PERF_SAMPLE_CGROUP feature Namhyung Kim
2020-01-07 13:34 [PATCHSET 0/9] perf: Improve cgroup profiling (v4) Namhyung Kim
2020-01-07 13:34 ` [PATCH 2/9] perf/core: Add PERF_SAMPLE_CGROUP feature Namhyung Kim
2020-03-25 12:45 [PATCHSET 0/9] perf: Improve cgroup profiling (v6) Namhyung Kim
2020-03-25 12:45 ` [PATCH 2/9] perf/core: Add PERF_SAMPLE_CGROUP feature Namhyung Kim

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