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--_000_0e42953988164786aafe175ef0f4e745xiaomicom_ Content-Type: text/html; charset="gb2312" Content-Transfer-Encoding: quoted-printable

Hi, Steve.


One accounting detail I would like to clarify before implementing this:
should buffers_mem and snapshot_buffers_mem include all memory owned by
the buffers, including slab-allocated ring-buffer metadata and reader
pages, or only the full pages backing the ring-buffer data?


My original lost-RAM use case primarily needs the non-slab page memory,
since slab is already accounted for separately. But I understand
"buffers_mem" and "total memory" may be intended to inc= lude both page
and slab allocations.


Thanks,
Xiang


=B7=A2=BC=FE=C8=CB: =B8=DF= =CF=E8
=B7=A2=CB=CD=CA=B1=BC=E4: 2026=C4=EA8=D4=C213=C8=D5 20:47:44
=CA=D5=BC=FE=C8=CB: Steven Rostedt
=B3=AD=CB=CD: Xiang Gao; Masami Hiramatsu; Mathieu Desnoyers; Lorenz= o Stoakes; gao xu; =D3=A1=B4=B3; linux-trace-kernel@vger.kernel.org; linux-= kernel@vger.kernel.org; linux-mm@kvack.org
=D6=F7=CC=E2: =B4=F0=B8=B4: [External Mail]Re: [RFC] tracing: aggreg= ate ring-buffer usage statistics
 

Thanks, Steve.

Understood.

I will add:

  /sys/kernel/tracing/trace_stats/total_memory_kb

The file will report:

  total:
  buffers_mem:
  snapshot_buffers_mem:

The values will cover the main and snapshot buffers of the global trac= e
array and all tracing instances across all tracing CPUs.

For the per-CPU view, I will follow the existing tracefs layout and ad= d:

  /sys/kernel/tracing/trace_stats/per_cpu/cpuN/total_memory_kb

Each per-CPU file will report only the corresponding CPU's buffers
across the global trace array and all tracing instances.

Thanks,
Xiang


=B7=A2=BC=FE=C8=CB: Steve= n Rostedt <rostedt@goodmis.org>
=B7=A2=CB=CD=CA=B1=BC=E4: 2026=C4=EA8=D4=C212=C8=D5 23:47:04
=CA=D5=BC=FE=C8=CB: =B8=DF=CF=E8
=B3=AD=CB=CD: Xiang Gao; Masami Hiramatsu; Mathieu Desnoyers; Lorenz= o Stoakes; gao xu; =D3=A1=B4=B3; linux-trace-kernel@vger.kernel.org; linux-= kernel@vger.kernel.org; linux-mm@kvack.org
=D6=F7=CC=E2: Re: [External Mail]Re: [RFC] tracing: aggregate ring-b= uffer usage statistics
 
[=CD=E2=B2=BF=D3=CA=BC=FE] =B4=CB=D3=CA=BC=FE=C0= =B4=D4=B4=D3=DA=D0=A1=C3=D7=B9=AB=CB=BE=CD=E2=B2=BF=A3=AC=C7=EB=BD=F7=C9=F7= =B4=A6=C0=ED=A1=A3=C8=F4=B6=D4=D3=CA=BC=FE=B0=B2=C8=AB=D0=D4=B4=E6=D2=C9=A3= =AC=C7=EB=BD=AB=D3=CA=BC=FE=D7=AA=B7=A2=B8=F8misec@xiaomi.com=BD=F8=D0=D0= =B7=B4=C0=A1

On Wed, 12 Aug 2026 13:21:29 +0000
=B8=DF=CF=E8 <gaoxiang17@xiaomi.com> wrote:

> Thanks, Steve.
>
> For the initial implementation, I plan to add:
>
>   /sys/kernel/tracing/trace_stats/total_memory_kb
>
> The file would use an extensible key/value format. Initially it would<= br> > report the ring-buffer data capacity:
>
>   total:        &nbs= p;          395664
>   ring_buffer:       &nbs= p;     395664
>   ring_buffer_live:       = ; 395544
>   ring_buffer_snapshot:       = 120

You can rename the above to:

   total:
   buffers_mem:
   snapshot_buffers_mem:

No need to use "ring" and it keeps consistent with "buffer_s= ize_kb".

I added the "mem" part to distinguish the difference between thes= e numbers
and the buffer_size_kb, as these numbers are about total memory whereas
the "buffer_size_kb" is about usable memory.

There's already a total for all memory listed. We don't need to have a
total for the "live" and "snapshot".

>
> Here, ring_buffer is the sum of ring_buffer_live and
> ring_buffer_snapshot. The values cover the global trace array and all<= br> > tracing instances across all tracing CPUs.
>
> Additional accounted categories, such as event memory, could be append= ed
> later and included in total. Per-CPU statistics could be exposed
> separately under trace_stats/per_cpu/cpuN/ to avoid mixing aggregate a= nd
> per-CPU values in one file.

Agreed, this file should exist in the cpuN/ directories and be only for
those instances.

>
> Userspace would parse fields by name and ignore unknown fields, so new=
> categories can be added without changing the existing format.

Right. I would expect additional items to be added here.

>
> Does this initial format look reasonable?
>

Yes, thanks for doing this.

-- Steve
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