From: "Michal Koutný" <mkoutny@suse.com>
To: ranxiaokai627@163.com
Cc: hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev,
shakeel.butt@linux.dev, muchun.song@linux.dev, tj@kernel.org,
shuah@kernel.org, kuba@kernel.org, hughd@google.com,
akpm@linux-foundation.org, cgroups@vger.kernel.org,
linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org, ran.xiaokai@zte.com.cn
Subject: Re: [PATCH 1/2] kselftests: cgroup: update kmem test tolerance for multi-memcg stock
Date: Wed, 15 Apr 2026 11:53:13 +0200 [thread overview]
Message-ID: <vjhou23d62pvtdqsan2nrlldkwf27qchpfmzf4yoetqn2gdhbj@cfiuqzzotbxf> (raw)
In-Reply-To: <20260414110524.2414-2-ranxiaokai627@163.com>
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Hello Xiaokai.
On Tue, Apr 14, 2026 at 11:05:23AM +0000, ranxiaokai627@163.com wrote:
> Fixes: f735eebe55f8 ("memcg: multi-memcg percpu charge cache")
An interesting catch.
> -#define MAX_VMSTAT_ERROR (4096 * 64 * get_nprocs())
> +#define NR_MEMCG_STOCK 7
> +#define MAX_VMSTAT_ERROR (4096 * 64 * NR_MEMCG_STOCK * get_nprocs())
When you touch this, I think this could be factored into it too:
+#define MAX_VMSTAT_ERROR (sysconf(_SC_PAGESIZE) * 64 * NR_MEMCG_STOCK * get_nprocs())
And given how much the selftest depends in this implementation
detail(?), I see that there are other selftests that include directly
from the tree, I'd suggest also
#include "../../../../include/linux/memcontrol.h"
and use the constant from there (i.e. move NR_MEMCG_STOCK to there too).
That should make the selftest more flexible, resilient to future changes
and it'd document ramification of these constants too.
Thanks,
Michal
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next prev parent reply other threads:[~2026-04-15 9:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-14 11:05 [PATCH 0/2] kselftests: cgroup: fix test_kmem false failures ranxiaokai627
2026-04-14 11:05 ` [PATCH 1/2] kselftests: cgroup: update kmem test tolerance for multi-memcg stock ranxiaokai627
2026-04-15 9:53 ` Michal Koutný [this message]
2026-04-15 11:03 ` ranxiaokai627
2026-04-14 11:05 ` [PATCH 2/2] kselftests: cgroup: account for slab memory in test_percpu_basic ranxiaokai627
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