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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 3/3] selftests: cgroup: Replace sleep with cg_read_key_long_poll() for waiting on nr_dying_descendants Message-ID: <3p7o2cxir6yz4baonmkrzumklg5zx3oddhi7mqlmxu26j7ze33@u2mrvj6pqad4> References: <20251124123816.486164-1-zhangguopeng@kylinos.cn> <20251124123816.486164-4-zhangguopeng@kylinos.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251124123816.486164-4-zhangguopeng@kylinos.cn> X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 52AA780006 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: sgkeszyzmrk97ddyuu4afrnrhxkmgcpj X-HE-Tag: 1764717534-149593 X-HE-Meta: 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 Rj6KLvFi DVeIyI4EJb9yHSbnSm1/zvLsMcxkty5k9qfpF74KL3B2S7Qa79Vf9YlkHREVzhH1tpFcQ9foOrvF0p/BDWvTMszTPK/ZWItLs5sQKrTIAWa+doZN+AHaZuhQOkWOpIdqz8NSbChFpOmoHN169/irKQVYafPOnwGq9+rc2vpflXcBjus+iUwLfCDgvitS0R5IzFZIvItugOING9vbzpGKHFNM9Vr8sZWxZp87wweNOegQcNgxnz/4cYgDzx+QWlEmoZi1O 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 08:38:16PM +0800, Guopeng Zhang wrote: > Replaced the manual sleep and retry logic in test_kmem_dead_cgroups() with the new > helper `cg_read_key_long_poll()`. This change improves the robustness of the test by > polling the "nr_dying_descendants" counter in `cgroup.stat` until it reaches 0 or the timeout is exceeded. > > Additionally, increased the retry timeout to 8 seconds (from 5 seconds) based on testing results: Why 8 seconds? What does it depend on? For memcg stats I see the 3 seconds driven from the 2 sec periodic rstat flush. Mainly how can we make this more future proof? > - With 5-second timeout: 4/20 runs passed. > - With 8-second timeout: 20/20 runs passed. > > Signed-off-by: Guopeng Zhang Anyways, just add a sentence in the commit message on the reasoning behind 8 seconds and a comment in code as well. With that, you can add: Reviewed-by: Shakeel Butt