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Date:   Wed, 7 Jun 2023 16:44:08 -0400
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Yosry Ahmed <yosryahmed@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Seth Jennings <sjenning@redhat.com>,
        Dan Streetman <ddstreet@ieee.org>,
        Vitaly Wool <vitaly.wool@konsulko.com>,
        Nhat Pham <nphamcs@gmail.com>,
        Domenico Cerasuolo <cerasuolodomenico@gmail.com>,
        Yu Zhao <yuzhao@google.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] mm: zswap: support exclusive loads
Message-ID: <20230607204408.GB340728@cmpxchg.org>
References: <20230607195143.1473802-1-yosryahmed@google.com>
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On Wed, Jun 07, 2023 at 07:51:43PM +0000, Yosry Ahmed wrote:
> Commit 71024cb4a0bf ("frontswap: remove frontswap_tmem_exclusive_gets")
> removed support for exclusive loads from frontswap as it was not used.
> Bring back exclusive loads support to frontswap by adding an "exclusive"
> output parameter to frontswap_ops->load.
> 
> On the zswap side, add a module parameter to enable/disable exclusive
> loads, and a config option to control the boot default value.
> Refactor zswap entry invalidation in zswap_frontswap_invalidate_page()
> into zswap_invalidate_entry() to reuse it in zswap_frontswap_load() if
> exclusive loads are enabled.
> 
> With exclusive loads, we avoid having two copies of the same page in
> memory (compressed & uncompressed) after faulting it in from zswap. On
> the other hand, if the page is to be reclaimed again without being
> dirtied, it will be re-compressed. Compression is not usually slow, and
> a page that was just faulted in is less likely to be reclaimed again
> soon.
> 
> Suggested-by: Yu Zhao <yuzhao@google.com>
> Signed-off-by: Yosry Ahmed <yosryahmed@google.com>

Thanks!

Acked-by: Johannes Weiner <hannes@cmpxchg.org>