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From: Shakeel Butt To: Guopeng Zhang 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 Subject: Re: [PATCH v4 2/3] selftests: cgroup: make test_memcg_sock robust against delayed sock stats Message-ID: References: <20251124123816.486164-1-zhangguopeng@kylinos.cn> <20251124123816.486164-3-zhangguopeng@kylinos.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251124123816.486164-3-zhangguopeng@kylinos.cn> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 71662140013 X-Stat-Signature: mginwy4nsk99uckk85d1exqrzshynt1r X-Rspam-User: X-HE-Tag: 1764717127-954349 X-HE-Meta: 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 ZAeYBak7 FZecFKQKI3cvMcrDOfUSXwsdz7oBljwfZAneY1VfS30z/Wfz5JjqfdL6LVdInpDf9LNOx7t1O5sXCDugkHD2LSbkDaitvL9qzeH9uMLkJFK87jU0080mjXG+asu2sYovxo0X1BlEloe/gR1/xsJCeO5tAupRs2FviLUWRBrlLUHW1D6Ep+G5iLDO7Ch122wXbwjSMsKavdbMTLxaUPpeQP/dWbFU1rT81MDGke4qpAn1XF59SosIx1hjpSqU7wRymvtAE 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 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