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Wed, 03 Dec 2025 11:27:50 +0800 Message-ID: <240ebe22-6e1c-4481-8a5e-b929bbfad178@kylinos.cn> Date: Wed, 3 Dec 2025 11:27:47 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/3] selftests: cgroup: make test_memcg_sock robust against delayed sock stats To: Shakeel Butt Cc: tj@kernel.org, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, mkoutny@suse.com, muchun.song@linux.dev, lance.yang@linux.dev, shuah@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20251124123816.486164-1-zhangguopeng@kylinos.cn> <20251124123816.486164-3-zhangguopeng@kylinos.cn> From: Guopeng Zhang In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 179F61C0007 X-Stat-Signature: 7c1cinpzzsy6rwsho44mzmk64j7stwub X-HE-Tag: 1764732475-642445 X-HE-Meta: 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 9auTfvIV rBTEMASdmgMpukzL/Sd07NfI8CrAlclBLIyK5X6OxDYjFtGHlX+aNOS0+ZnZH3g+AcQHEi7kIkSFMh/DoiuNuhXApfSeM6Etr1tP/xbMkbIAXJaH7go2VSvzSBsZNyA+WwaOU X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 12/3/25 07:12, Shakeel Butt wrote: > On Mon, Nov 24, 2025 at 08:38:15PM +0800, Guopeng Zhang wrote: >> test_memcg_sock() currently requires that memory.stat's "sock " counter >> is exactly zero immediately after the TCP server exits. On a busy system >> this assumption is too strict: >> >> - Socket memory may be freed with a small delay (e.g. RCU callbacks). >> - memcg statistics are updated asynchronously via the rstat flushing >> worker, so the "sock " value in memory.stat can stay non-zero for a >> short period of time even after all socket memory has been uncharged. >> >> As a result, test_memcg_sock() can intermittently fail even though socket >> memory accounting is working correctly. >> >> Make the test more robust by polling memory.stat for the "sock " >> counter and allowing it some time to drop to zero instead of checking >> it only once. The timeout is set to 3 seconds to cover the periodic >> rstat flush interval (FLUSH_TIME = 2*HZ by default) plus some >> scheduling slack. If the counter does not become zero within the >> timeout, the test still fails as before. >> >> On my test system, running test_memcontrol 50 times produced: >> >> - Before this patch: 6/50 runs passed. >> - After this patch: 50/50 runs passed. >> >> Signed-off-by: Guopeng Zhang >> Suggested-by: Lance Yang >> --- >> .../selftests/cgroup/test_memcontrol.c | 20 ++++++++++++++++++- >> 1 file changed, 19 insertions(+), 1 deletion(-) >> >> diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c >> index 4e1647568c5b..dda12e5c6457 100644 >> --- a/tools/testing/selftests/cgroup/test_memcontrol.c >> +++ b/tools/testing/selftests/cgroup/test_memcontrol.c >> @@ -21,6 +21,8 @@ >> #include "kselftest.h" >> #include "cgroup_util.h" >> >> +#define MEMCG_SOCKSTAT_WAIT_RETRIES 30 /* 3s total */ > > No need for the comment at the end as it will be stale when someone > change DEFAULT_WAIT_INTERVAL_US in future. > > Anyways it's a nit. > > Reviewed-by: Shakeel Butt Hi Shakeel, Thanks for the review and for the Reviewed-by. Good point about the comment. I’ll drop the "/* 3s total */" part in the next version so it does not become stale if DEFAULT_WAIT_INTERVAL_US changes. Thanks, Guopeng