linux-kernel - Re: [PATCH v2] mm/codetag: swap tags when migrate pages

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Message-ID: <CAOUHufZpr9GR2KLpgYNMkzBptp3OGDZuHs8URtnKHyU0eap6xg@mail.gmail.com>
Date: Mon, 2 Dec 2024 15:19:29 -0700
From: Yu Zhao <yuzhao@...gle.com>
To: David Wang <00107082@....com>
Cc: surenb@...gle.com, kent.overstreet@...ux.dev, akpm@...ux-foundation.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/codetag: swap tags when migrate pages

On Thu, Nov 28, 2024 at 7:52 PM David Wang <00107082@....com> wrote:
>
> Current solution to adjust codetag references during page migration is
> done in 3 steps:
> 1. sets the codetag reference of the old page as empty (not pointing
> to any codetag);
> 2. subtracts counters of the new page to compensate for its own allocation;
> 3. sets codetag reference of the new page to point to the codetag of
> the old page.
> This does not work if CONFIG_MEM_ALLOC_PROFILING_DEBUG=n because
> set_codetag_empty() becomes NOOP. Instead, let's simply swap codetag
> references so that the new page is referencing the old codetag and the
> old page is referencing the new codetag. This way accounting stays
> valid and the logic makes more sense.
>
> Fixes: e0a955bf7f61 ("mm/codetag: add pgalloc_tag_copy()")
> Signed-off-by: David Wang <00107082@....com>
> Closes: https://lore.kernel.org/lkml/20241124074318.399027-1-00107082@163.com/
> Acked-by: Suren Baghdasaryan <surenb@...gle.com>
> Suggested-by: Suren Baghdasaryan <surenb@...gle.com>

Acked-by: Yu Zhao <yuzhao@...gle.com>