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

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Message-ID: <Z32EFouwz3IHw8h0@x1>
Date: Tue, 7 Jan 2025 16:44:22 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>,
	Chun-Tse Shao <ctshao@...gle.com>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	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 Wed, Nov 06, 2024 at 12:30:06AM +0000, 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:

I applied the first patch in the series, that already helps, Peter, what
about this one for the kernel?

- Arnaldo
 
>   $ ./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>
> 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);
> +}
> +
>  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