linux-kernel - Re: [PATCH v5 5/8] mm/shmem, swap: never use swap cache and readahead for SWP_SYNCHRONOUS

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Message-ID: <1fe97413-03eb-433a-91b3-b53e58c65622@linux.alibaba.com>
Date: Fri, 11 Jul 2025 14:10:00 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Kairui Song <kasong@...cent.com>, linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>, Hugh Dickins
 <hughd@...gle.com>, Matthew Wilcox <willy@...radead.org>,
 Kemeng Shi <shikemeng@...weicloud.com>, Chris Li <chrisl@...nel.org>,
 Nhat Pham <nphamcs@...il.com>, Baoquan He <bhe@...hat.com>,
 Barry Song <baohua@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 5/8] mm/shmem, swap: never use swap cache and readahead
 for SWP_SYNCHRONOUS_IO



On 2025/7/10 11:37, Kairui Song wrote:
> From: Kairui Song <kasong@...cent.com>
> 
> For SWP_SYNCHRONOUS_IO devices, if a cache bypassing THP swapin failed
> due to reasons like memory pressure, partially conflicting swap cache
> or ZSWAP enabled, shmem will fallback to cached order 0 swapin.
> 
> Right now the swap cache still has a non-trivial overhead, and readahead
> is not helpful for SWP_SYNCHRONOUS_IO devices, so we should always skip
> the readahead and swap cache even if the swapin falls back to order 0.
> 
> So handle the fallback logic without falling back to the cached read.
> 
> Signed-off-by: Kairui Song <kasong@...cent.com>

LGTM. Thanks.
Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>