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

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Message-ID: <CAJuCfpFSYqQ1LN0OZQT+jU=vLXZa5-L2Agdk1gzMdk9J0Zb-vg@mail.gmail.com>
Date: Thu, 26 Dec 2024 15:07:39 -0800
From: Suren Baghdasaryan <surenb@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
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 Thu, Dec 26, 2024 at 3:01 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Thu, 26 Dec 2024 13:16:39 -0800 Suren Baghdasaryan <surenb@...gle.com> wrote:
>
> > When memory allocation profiling is disabled, there is no need to swap
> > allocation tags during migration. Skip it to avoid unnecessary overhead.
> >
> > Fixes: e0a955bf7f61 ("mm/codetag: add pgalloc_tag_copy()")
> > Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
> > Cc: stable@...r.kernel.org
>
> Are these changes worth backporting?  Some indication of how much
> difference the patches make would help people understand why we're
> proposing a backport.

The first patch ("alloc_tag: avoid current->alloc_tag manipulations
when profiling is disabled") I think is worth backporting. It
eliminates about half of the regression for slab allocations when
profiling is disabled. The second one I couldn't really measure, so I
think it's not as important. Thanks!

>