linux-kernel - Re: selftests: cgroup: Failures – Timeouts & OOM Issues Analysis

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Message-ID: <twi33lxboes5lvflguqik23dlehvwczee2gvsbllrz3gbtb7wl@w23lqyocl6p3>
Date: Mon, 14 Apr 2025 15:46:39 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Naresh Kamboju <naresh.kamboju@...aro.org>
Cc: Cgroups <cgroups@...r.kernel.org>, linux-mm <linux-mm@...ck.org>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
Subject: Re: selftests: cgroup: Failures – Timeouts & OOM Issues Analysis

-Cc: non-lists

On Tue, Mar 04, 2025 at 03:20:58PM +0100, Michal Koutný <mkoutny@...e.com> wrote:
> Actually, I noticed test_memcontrol failure yesterday (with ~mainline
> kernel) but I remember they used to work also rather recently. I haven't
> got time to look into that but at least that one may be a regression (in
> code or test).

So I'm seeing (with v6.15-rc1):

| not ok 1 test_kmem_basic
| ok 2 test_kmem_memcg_deletion
| ok 3 test_kmem_proc_kpagecgroup
| ok 4 test_kmem_kernel_stacks
| not ok 5 test_kmem_dead_cgroups
| memory.current 8130560 [ <- 1 vCPU ] 13168640
| percpu         5040000 [ 4 vCPUs ->] 10080000
| not ok 6 test_percpu_basic

not ok 1
By a quick look I suspect that negative dentries that are used to boost
memory consumption aren't enough (since some kernel changes, test
assumes at least 10B/dentry) -- presumably inappropriate test in new
dentry environment, not memcg bug proper.

not ok 5
A dying memcg pinned by something indefinitely, didn't look deeper into
that. Little suspicious.

not ok 6
That looks like the test doesn't take into account non-percpu
allocations of memcg (e.g. struct memcg alone is a ~2KiB + struct
mem_cgroup_per_node). The test needs better boundaries, not a memcg bug.

HTH,
Michal

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