linux-kernel - Re: [RFC PATCH 5/9] mm: zswap: remove zswap_same_filled_pages

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Date: Tue, 26 Mar 2024 15:01:18 -0700
From: Nhat Pham <nphamcs@...il.com>
To: Yosry Ahmed <yosryahmed@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Johannes Weiner <hannes@...xchg.org>, 
	Chengming Zhou <chengming.zhou@...ux.dev>, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 5/9] mm: zswap: remove zswap_same_filled_pages_enabled

On Mon, Mar 25, 2024 at 4:50 PM Yosry Ahmed <yosryahmed@...gle.com> wrote:
>
> There is no logical reason to refuse storing same-filled pages more
> efficiently and opt for compression. Remove the userspace knob.
>

Agree. Absolutely no idea why we have this knob in the first place -
if you have cycles to compress, you probably have some extra cycles to
check same-filled page state? And that is the only cost I can think of
- it wins on probably all other aspects: memory usage,
"decompression", no need to write back these pages etc.

Any actual zswap user who has data or counter-use case should chime
in, but FWIW, my vote is:
Reviewed-by: Nhat Pham <nphamcs@...il.com>