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Thanks for the suggestion.


The original motivation is Android lost-RAM attribution. Ftrace
ring-buffer data pages are not represented as a separate memory
category, so userspace can count them as lost RAM.


The buffers can be spread across the global trace array, multiple
instances, and snapshot buffers. Userspace currently has to discover
and sum every instance, and snapshot capacity is not available through
the same per-instance total. On one Android device, the global buffer
and 24 instances accounted for 395,664 kB, so the missing attribution
was significant.


I agree that /proc/meminfo is not the right interface. I will rework
this as an RFC under tracefs, with the tracing memory usage broken down
by category.


Thanks.


=B7=A2=BC=FE=C8=CB: Steve= n Rostedt <rostedt@goodmis.org>
=B7=A2=CB=CD=CA=B1=BC=E4: 2026=C4=EA8=D4=C210=C8=D5 22:57:10
=CA=D5=BC=FE=C8=CB: Lorenzo Stoakes (ARM)
=B3=AD=CB=CD: David Hildenbrand (Arm); Xiang Gao; Andrew Morton; Mas= ami Hiramatsu; Mathieu Desnoyers; liam@infradead.org; Vlastimil Babka; Mike= Rapoport; Suren Baghdasaryan; Michal Hocko; linux-trace-kernel@vger.kernel= .org; linux-mm@kvack.org; linux-fsdevel@vger.kernel.org; linux-kernel@vger.kernel.org; =B8=DF=CF=E8
=D6=F7=CC=E2: [External Mail]Re: [PATCH] tracing: report buffer memo= ry in /proc/meminfo
 
[=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 Mon, 10 Aug 2026 12:22:43 +0100
"Lorenzo Stoakes (ARM)" <ljs@kernel.org> wrote:

> On Mon, Aug 10, 2026 at 12:52:38PM +0200, David Hildenbrand (Arm) = wrote:
> > On 8/10/26 11:40, Xiang Gao wrote:
> > > Report the data capacity of all ftrace ring buffers through = a new Ftrace
> > > field in /proc/meminfo. Include the main and snapshot buffer= s of the
> > > global trace array and all tracing instances, while leaving = ring-buffer
> > > metadata accounted for by Slab.
> >
> > why? :)
> >
> > To report a handful of KiB as in your example below? Doesn't soun= d super helpful
> > TBH.
>
> Yeah I think we need to stop with all the proposed additions to /proc/= meminfo :)
>
> Also something like this where you are making a change in output that = it is just
> your opinion that it is useful should be an RFC to see what the commun= ity thinks
> first.

Agreed. This doesn't belong in the meminfo. If you want memory statistics for tracing, I may be OK if you add a "total_memory_kb" file in t= he
/sys/kernel/tracing/trace_stats/ directory.

And break it up for memory used. Ring buffers, events, etc.

Perhaps even add one per CPU as well.

I'm always conscience about how much memory tracing is taking up in the
system.

-- Steve
 --_000_b1378a355ce648a7b994d1ec8d56f10dxiaomicom_--