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

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Message-ID: <CAP-5=fUc0YttVUMB9oAit3u5hzVGuK5rTLnP_dXD0kqt7QcO5g@mail.gmail.com>
Date: Thu, 14 Nov 2024 07:49:44 -0800
From: Ian Rogers <irogers@...gle.com>
To: Chun-Tse Shao <ctshao@...gle.com>
Cc: linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.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
Subject: Re: [PATCH v3 2/3] perf: Reveal PMU type in fdinfo

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 process.
> 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.

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
>