linux-kernel - [RFC PATCH 0/1] zram: Allow rw_page when page isn't written back.

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Message-Id: <20220808165006.2451180-1-bgeffon@google.com>
Date:   Mon,  8 Aug 2022 12:50:05 -0400
From:   Brian Geffon <bgeffon@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Minchan Kim <minchan@...nel.org>
Cc:     Nitin Gupta <ngupta@...are.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        linux-kernel@...r.kernel.org,
        Suleiman Souhlal <suleiman@...gle.com>, linux-mm@...ck.org,
        Brian Geffon <bgeffon@...gle.com>
Subject: [RFC PATCH 0/1] zram: Allow rw_page when page isn't written back.

Today when a zram device has a backing device we change the ops to
a new set which does not expose a rw_page method. This prevents the
upper layers from trying to issue a synchronous rw. This has the
downside that we penalize every rw even when it could possibly
still be performed as a synchronous rw.

This is just a proposal and I wanted to get feedback if people
felt this was worthwhile.

The motivation comes from what Minchan noted in the original
change which introduced the synchronous behavior that it enhanches
swap-in performance by about 45% [1]. So it'd be great if we could
still get this benefit while using writeback.

1. https://lore.kernel.org/all/1505886205-9671-5-git-send-email-minchan@kernel.org/

Brian Geffon (1):
  zram: Allow rw_page when page isn't written back.

 drivers/block/zram/zram_drv.c | 65 +++++++++++++++++++++--------------
 drivers/block/zram/zram_drv.h |  1 +
 2 files changed, 41 insertions(+), 25 deletions(-)

-- 
2.37.1.559.g78731f0fdb-goog