linux-kernel - Re: [PATCH 2/2] alloc_tag: skip pgalloc_tag

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Message-Id: <20250114171045.e5fadb8db51902ee0181fa0b@linux-foundation.org>
Date: Tue, 14 Jan 2025 17:10:45 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: kent.overstreet@...ux.dev, yuzhao@...gle.com, 00107082@....com,
 quic_zhenhuah@...cinc.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 2/2] alloc_tag: skip pgalloc_tag_swap if profiling is
 disabled

On Tue, 14 Jan 2025 08:38:37 -0800 Suren Baghdasaryan <surenb@...gle.com> wrote:

> > > Well, a 50% reduction in a 0.0000000001% overhead ain't much.
> >
> > I wish the overhead was that low :)
> >
> > I ran more comprehensive testing on Pixel 6 on Big, Medium and Little cores:
> >
> >                  Overhead before fixes            Overhead after fixes
> >                  slab alloc      page alloc          slab alloc      page alloc
> > Big               6.21%           5.32%                3.31%          4.93%
> > Medium       4.51%           5.05%                3.79%          4.39%
> > Little            7.62%           1.82%                6.68%          1.02%
> 
> Hi Andrew,
> I just noticed that you added the above results to the description of
> this patch in mm-unstable: 366507569511 ("alloc_tag: skip
> pgalloc_tag_swap if profiling is disabled") but this improvement is
> mostly caused the the other patch in this series: 80aded2b9492
> ("alloc_tag: avoid current->alloc_tag manipulations when profiling is
> disabled"). If this is not too much trouble, could you please move it
> into the description of the latter patch?

No probs, done, thanks.