linux-kernel - Re: [PATCH v4 1/2] perf: Reveal PMU type in fdinfo

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Message-ID: <9413e707-35d2-4c9a-9058-d14112ebb2cc@linux.intel.com>
Date: Tue, 30 Sep 2025 11:12:07 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Chun-Tse Shao <ctshao@...gle.com>, linux-kernel@...r.kernel.org
Cc: Ian Rogers <irogers@...gle.com>, peterz@...radead.org, mingo@...hat.com,
 acme@...nel.org, namhyung@...nel.org, mark.rutland@....com,
 alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
 adrian.hunter@...el.com, kan.liang@...ux.intel.com, james.clark@...aro.org,
 howardchu95@...il.com, weilin.wang@...el.com,
 linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v4 1/2] perf: Reveal PMU type in fdinfo


On 6/4/2025 2:15 AM, Chun-Tse Shao 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
>
> Reviewed-by: Ian Rogers <irogers@...gle.com>
> Signed-off-by: Chun-Tse Shao <ctshao@...gle.com>
> ---
> v4:
>   Removed the first patch in v3 since it is merged.
>   Retested to make sure the patch still work.
>
> v3: lore.kernel.org/20241106003007.2112584-2-ctshao@...gle.com
>
>  kernel/events/core.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 95e703891b24..bad563692d63 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -56,6 +56,7 @@
>  #include <linux/buildid.h>
>  #include <linux/task_work.h>
>  #include <linux/percpu-rwsem.h>
> +#include <linux/seq_file.h>
>
>  #include "internal.h"
>
> @@ -7077,6 +7078,14 @@ 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);

Could we print the config field with hexadecimal format? It makes the event
is more easily recognized. Thanks.


> +}
> +
>  static const struct file_operations perf_fops = {
>  	.release		= perf_release,
>  	.read			= perf_read,
> @@ -7085,6 +7094,7 @@ static const struct file_operations perf_fops = {
>  	.compat_ioctl		= perf_compat_ioctl,
>  	.mmap			= perf_mmap,
>  	.fasync			= perf_fasync,
> +	.show_fdinfo		= perf_show_fdinfo,
>  };
>
>  /*
> --
> 2.49.0.1204.g71687c7c1d-goog
>
>