linux-kernel - Re: [PATCH v2 2/2] selftests/cgroup: add test for zswap incompressible pages

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Message-ID: <aYYvNq0CibG_ABEG@linux.dev>
Date: Fri, 6 Feb 2026 10:13:33 -0800
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Jiayuan Chen <jiayuan.chen@...ux.dev>
Cc: linux-mm@...ck.org, Jiayuan Chen <jiayuan.chen@...pee.com>, 
	Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
	Michal Koutný <mkoutny@...e.com>, Jonathan Corbet <corbet@....net>, 
	Michal Hocko <mhocko@...nel.org>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Muchun Song <muchun.song@...ux.dev>, Andrew Morton <akpm@...ux-foundation.org>, 
	Yosry Ahmed <yosry.ahmed@...ux.dev>, Nhat Pham <nphamcs@...il.com>, 
	Chengming Zhou <chengming.zhou@...ux.dev>, Shuah Khan <shuah@...nel.org>, cgroups@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 2/2] selftests/cgroup: add test for zswap
 incompressible pages

On Fri, Feb 06, 2026 at 03:22:16PM +0800, Jiayuan Chen wrote:
> From: Jiayuan Chen <jiayuan.chen@...pee.com>
> 
> Add test_zswap_incompressible() to verify that the zswap_incomp memcg
> stat correctly tracks incompressible pages.
> 
> The test allocates memory filled with random data from /dev/urandom,
> which cannot be effectively compressed by zswap. When this data is
> swapped out to zswap, it should be stored as-is and tracked by the
> zswap_incomp counter.
> 
> The test verifies that:
> 1. Pages are swapped out to zswap (zswpout increases)
> 2. Incompressible pages are tracked (zswap_incomp increases)
> 
> test:
> dd if=/dev/zero of=/swapfile bs=1M count=2048
> chmod 600 /swapfile
> mkswap /swapfile
> swapon /swapfile
> echo Y > /sys/module/zswap/parameters/enabled
> 
> ./test_zswap
>  TAP version 13
>  1..8
>  ok 1 test_zswap_usage
>  ok 2 test_swapin_nozswap
>  ok 3 test_zswapin
>  ok 4 test_zswap_writeback_enabled
>  ok 5 test_zswap_writeback_disabled
>  ok 6 test_no_kmem_bypass
>  ok 7 test_no_invasive_cgroup_shrink
>  ok 8 test_zswap_incompressible
>  Totals: pass:8 fail:0 xfail:0 xpass:0 skip:0 error:0
> 
> Signed-off-by: Jiayuan Chen <jiayuan.chen@...pee.com>

Acked-by: Shakeel Butt <shakeel.butt@...ux.dev>