Re: [PATCH 2/3] perf: Reveal PMU type in fdinfo

[Ian Rogers <irogers@google.com>]

On Thu, Oct 31, 2024 at 3:39 PM Chun-Tse Shao <ctshao@google.com> wrote:
>
> It gives useful info on knowing which PMUs are reserved by this process.
> Also add extra attributes 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-orig_type:   0

nit: I think this should be:
perf_event-type:   0
this output was from an earlier version.

> perf_event-attr.config1:        0
> perf_event-attr.config2:        0
> perf_event-attr.config3:        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
> perf_event-attr.config1:        0
> perf_event-attr.config2:        0
> perf_event-attr.config3:        0
> ```
>
> Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> ---
>  kernel/events/core.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index cdd09769e6c56..e0891c376fd9d 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -8,6 +8,7 @@
>   *  Copyright  ©  2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
>   */
>
> +#include "linux/seq_file.h"

nit: I think you should use angle < > rather than quotes on the
include for consistency.

Thanks,
Ian

>  #include <linux/fs.h>
>  #include <linux/mm.h>
>  #include <linux/cpu.h>
> @@ -6820,6 +6821,17 @@ 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", event->attr.config);
> +       seq_printf(m, "perf_event-attr.config1:\t%llu\n", event->attr.config1);
> +       seq_printf(m, "perf_event-attr.config2:\t%llu\n", event->attr.config2);
> +       seq_printf(m, "perf_event-attr.config3:\t%llu\n", event->attr.config3);
> +}
> +
>  static const struct file_operations perf_fops = {
>         .release                = perf_release,
>         .read                   = perf_read,
> @@ -6828,6 +6840,7 @@ static const struct file_operations perf_fops = {
>         .compat_ioctl           = perf_compat_ioctl,
>         .mmap                   = perf_mmap,
>         .fasync                 = perf_fasync,
> +       .show_fdinfo            = perf_show_fdinfo,
>  };
>
>  /*
> --
> 2.47.0.163.g1226f6d8fa-goog
>