linux-kernel - Re: [PATCH] Add accumulated call counter for memory allocation profiling

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Message-ID: <CAJuCfpGaEJLaWYPidiAG1vtayugQY5vJoFv9Opauh1TrofOv7Q@mail.gmail.com>
Date: Sun, 30 Jun 2024 12:33:14 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: David Wang <00107082@....com>
Cc: kent.overstreet@...ux.dev, akpm@...ux-foundation.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Add accumulated call counter for memory allocation profiling

On Mon, Jun 17, 2024 at 8:33 AM David Wang <00107082@....com> wrote:
>
> Accumulated call counter can be used to evaluate rate
> of memory allocation via delta(counters)/delta(time).
> This metrics can help analysis performance behaviours,
> e.g. tuning cache size, etc.

Sorry for the delay, David.
IIUC with this counter you can identify the number of allocations ever
made from a specific code location. Could you please clarify the usage
a bit more? Is the goal to see which locations are the most active and
the rate at which allocations are made there? How will that
information be used?
I'm a bit cautious here because each counter will take more space and
use some additional cpu cycles.
Thanks,
Suren.

>
> Signed-off-by: David Wang <00107082@....com>
> ---
>  include/linux/alloc_tag.h | 11 +++++++----
>  lib/alloc_tag.c           |  7 +++----
>  2 files changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
> index abd24016a900..62734244c0b9 100644
> --- a/include/linux/alloc_tag.h
> +++ b/include/linux/alloc_tag.h
> @@ -18,6 +18,7 @@
>  struct alloc_tag_counters {
>         u64 bytes;
>         u64 calls;
> +       u64 accu_calls;
>  };
>
>  /*
> @@ -102,14 +103,15 @@ static inline bool mem_alloc_profiling_enabled(void)
>
>  static inline struct alloc_tag_counters alloc_tag_read(struct alloc_tag *tag)
>  {
> -       struct alloc_tag_counters v = { 0, 0 };
> +       struct alloc_tag_counters v = { 0, 0, 0 };
>         struct alloc_tag_counters *counter;
>         int cpu;
>
>         for_each_possible_cpu(cpu) {
> -               counter = per_cpu_ptr(tag->counters, cpu);
> -               v.bytes += counter->bytes;
> -               v.calls += counter->calls;
> +               counter         = per_cpu_ptr(tag->counters, cpu);
> +               v.bytes         += counter->bytes;
> +               v.calls         += counter->calls;
> +               v.accu_calls    += counter->accu_calls;
>         }
>
>         return v;
> @@ -145,6 +147,7 @@ static inline void __alloc_tag_ref_set(union codetag_ref *ref, struct alloc_tag
>          * counter because when we free each part the counter will be decremented.
>          */
>         this_cpu_inc(tag->counters->calls);
> +       this_cpu_inc(tag->counters->accu_calls);
>  }
>
>  static inline void alloc_tag_ref_set(union codetag_ref *ref, struct alloc_tag *tag)
> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> index 11ed973ac359..c4059362d828 100644
> --- a/lib/alloc_tag.c
> +++ b/lib/alloc_tag.c
> @@ -66,8 +66,8 @@ static void allocinfo_stop(struct seq_file *m, void *arg)
>  static void print_allocinfo_header(struct seq_buf *buf)
>  {
>         /* Output format version, so we can change it. */
> -       seq_buf_printf(buf, "allocinfo - version: 1.0\n");
> -       seq_buf_printf(buf, "#     <size>  <calls> <tag info>\n");
> +       seq_buf_printf(buf, "allocinfo - version: 1.1\n");
> +       seq_buf_printf(buf, "#     <size>  <calls> <tag info> <accumulated calls>\n");
>  }
>
>  static void alloc_tag_to_text(struct seq_buf *out, struct codetag *ct)
> @@ -78,8 +78,7 @@ static void alloc_tag_to_text(struct seq_buf *out, struct codetag *ct)
>
>         seq_buf_printf(out, "%12lli %8llu ", bytes, counter.calls);
>         codetag_to_text(out, ct);
> -       seq_buf_putc(out, ' ');
> -       seq_buf_putc(out, '\n');
> +       seq_buf_printf(out, " %llu\n", counter.accu_calls);
>  }
>
>  static int allocinfo_show(struct seq_file *m, void *arg)
> --
> 2.39.2
>