linux-kernel - Re: [PATCH v3 2/3] perf: Reveal PMU type in fdinfo

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Message-ID: <CAJpZYjUDKxdLEfYJ3TdOz3N5m5R=et7P01a+K8UNpdgjYe3R=Q@mail.gmail.com>
Date: Wed, 18 Dec 2024 21:37:49 -0800
From: Chun-Tse Shao <ctshao@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	Ze Gao <zegao2021@...il.com>, Weilin Wang <weilin.wang@...el.com>, 
	linux-perf-users@...r.kernel.org, Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH v3 2/3] perf: Reveal PMU type in fdinfo

Hi Peter, just want to bring your attention to this patch since you
left comments on the previous version of patch.

Thanks,
CT

On Thu, Nov 21, 2024 at 1:18 PM Chun-Tse Shao <ctshao@...gle.com> wrote:
>
> Hi, just a friendly ping for review, in case anyone missed this.
>
> Thanks,
> CT
>
> On Thu, Nov 14, 2024 at 10:30 AM Chun-Tse Shao <ctshao@...gle.com> wrote:
> >
> > Hi Ian,
> >
> > On Thu, Nov 14, 2024 at 7:49 AM Ian Rogers <irogers@...gle.com> wrote:
> > >
> > > On Tue, Nov 5, 2024 at 4:30 PM Chun-Tse Shao <ctshao@...gle.com> wrote:
> > > >
> > > > It gives useful info on knowing which PMUs are reserved by this proceszs.
> > > > Also add config which would be useful.
> > > > Testing cycles:
> > > >
> > > >   $ ./perf stat -e cycles &
> > > >   $ cat /proc/`pidof perf`/fdinfo/3
> > > >   pos:    0
> > > >   flags:  02000002
> > > >   mnt_id: 16
> > > >   ino:    3081
> > > >   perf_event_attr.type:   0
> > > >   perf_event_attr.config: 0
> > > >
> > > > Testing L1-dcache-load-misses:
> > > >
> > > >   $ ./perf stat -e L1-dcache-load-misses &
> > > >   $ cat /proc/`pidof perf`/fdinfo/3
> > > >   pos:    0
> > > >   flags:  02000002
> > > >   mnt_id: 16
> > > >   ino:    1072
> > > >   perf_event_attr.type:   3
> > > >   perf_event_attr.config: 65536
> > > >
> > > > Signed-off-by: Chun-Tse Shao <ctshao@...gle.com>
> > >
> > > Reviewed-by: Ian Rogers <irogers@...gle.com>
> > >
> > > > Change-Id: Ibea5618aaf00bae6f48a9b2a6e7798ab2b7f23ce
> > > > ---
> > > >  kernel/events/core.c | 10 ++++++++++
> > > >  1 file changed, 10 insertions(+)
> > > >
> > > > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > > > index cdd09769e6c56..398cac8b208b9 100644
> > > > --- a/kernel/events/core.c
> > > > +++ b/kernel/events/core.c
> > > > @@ -55,6 +55,7 @@
> > > >  #include <linux/pgtable.h>
> > > >  #include <linux/buildid.h>
> > > >  #include <linux/task_work.h>
> > > > +#include <linux/seq_file.h>
> > > >
> > > >  #include "internal.h"
> > > >
> > > > @@ -6820,6 +6821,14 @@ static int perf_fasync(int fd, struct file *filp, int on)
> > > >         return 0;
> > > >  }
> > > >
> > > > +static void perf_show_fdinfo(struct seq_file *m, struct file *f)
> > > > +{
> > > > +       struct perf_event *event = f->private_data;
> > > > +
> > > > +       seq_printf(m, "perf_event_attr.type:\t%u\n", event->orig_type);
> > > > +       seq_printf(m, "perf_event_attr.config:\t%llu\n", (unsigned long long)event->attr.config);
> > >
> > > nit: is the cast necessary? I don't see __u64 listed on:
> > > https://www.kernel.org/doc/Documentation/printk-formats.txt
> > > so I'm unsure.
> > >
> >
> > In this case I think it is safer to cast it to `unsigned long long`,
> > since I don't know if any architecture would have an exception on
> > __u64.
> >
> > Thanks,
> > CT
> >
> > > Thanks,
> > > Ian
> > >
> > > > +}
> > > > +
> > > >  static const struct file_operations perf_fops = {
> > > >         .release                = perf_release,
> > > >         .read                   = perf_read,
> > > > @@ -6828,6 +6837,7 @@ static const struct file_operations perf_fops = {
> > > >         .compat_ioctl           = perf_compat_ioctl,
> > > >         .mmap                   = perf_mmap,
> > > >         .fasync                 = perf_fasync,
> > > > +       .show_fdinfo            = perf_show_fdinfo,
> > > >  };
> > > >
> > > >  /*
> > > > --
> > > > 2.47.0.199.ga7371fff76-goog
> > > >