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AJvYcCV4fuX3J7bHUzyshKcia74qLeu3HiSSp2FcnW4lpBcz1XV+TmsNrkoCMQC2d2sH/AgviSqhZws1Yg==@kvack.org X-Gm-Message-State: AOJu0YwfoIJuBXi1zRRmgu/NWxex0JyEUZLDjU3DP+uDWE1WIinv2NYE X7l+E6A+tYn6eYMurPn04dztN+/Di4u+4FMWbwt1UgXasp50zPeuKyHqZ/J26dQSrAXXW6yBd0s FD7txcsR60vVYBMexg2C0AbkS/FERa1vutX09UdDBNg== X-Gm-Gg: ASbGncvOPJCRmdSBP2A7xg7Npa0iqqhsrRj2DeD0Zsicz2lXBbQBxQgMtPaohsMrPQt URNYIKBodBLXly4Fm8FSHtyBGayqEWMGSJdSGMgK54huYV/SFTRcfFJ9ZAFxRf+Snu/vBcmwPOZ hg1WXVI8RXb+EiFf3/t7V8PUsVJVM1dp0nV2pHH5E+1pC9U6tVOfhxNBqn+X+1Gkbzh0kJipAUG SGPQbN/l/DPT8vRKPOQqefpJ3UZJsTc9K3KkCNTgxB6UsbQA4RVHMVAVwvCU9QHGgFoEA== X-Google-Smtp-Source: AGHT+IFd4ZD8LO3gWA0tYoGo49H3rk4bG8UV2Nu8f5cyi48eyODapZFusRvqrzWLi1Ytu9FzHhwORQyO09cagbntAK0= X-Received: by 2002:a17:907:7f01:b0:b73:70db:49ab with SMTP id a640c23a62f3a-b76553fa23bmr176598566b.35.1763617231293; Wed, 19 Nov 2025 21:40:31 -0800 (PST) MIME-Version: 1.0 References: <20251119105216.1675608-1-zhangguopeng@kylinos.cn> <20251119122758.85610-1-ioworker0@gmail.com> <2c276ed9-626f-4bae-9d42-727dd176ec74@kylinos.cn> In-Reply-To: <2c276ed9-626f-4bae-9d42-727dd176ec74@kylinos.cn> From: Leon Huang Fu Date: Thu, 20 Nov 2025 13:39:53 +0800 X-Gm-Features: AWmQ_bmEoAEKzhLFdmzN3VkYMFPpl9dZhwR3SWWzVK97oW1lQq-769I_C_Td8qw Message-ID: Subject: Re: [PATCH] selftests: cgroup: make test_memcg_sock robust against delayed sock stats To: Guopeng Zhang Cc: Lance Yang , hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, mkoutny@suse.com, muchun.song@linux.dev, roman.gushchin@linux.dev, shakeel.butt@linux.dev, shuah@kernel.org, tj@kernel.org, Lance Yang Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: CFAE5A0006 X-Stat-Signature: ycyrb91wcrwked35pib4nmr5us3srdp5 X-Rspam-User: X-HE-Tag: 1763617232-590071 X-HE-Meta: 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 s8zipBPl pZZV/hEYds6F652JOMaV0XVIpJohYatM9qRGvdSYRkI0D7V+Y/HpzI0OvVSj4BAi9UYVxr2RDsiyDAEdzhlB4Y0P+1bUZc4V0kEKXTLGTDX3y49Xv9rKgEB5kkRUHm23/2nb6SQS+WPkOI+aaBiNQfswyksKP+VNlP7RzMlhfp+mMRINpnY/zguwbDtRNKUCGzRAGXvXW6pSy5PyBq0g04zrrtd5wNWld5Q6y31pqW/9DwgHqKdlT4U4qLhI5F6I4b8rFg+EREyTlMLdAJSBYErA8aIS2OChCrfNhTOlRm5uw2lL9g232RUOoFISnU8GKJ2VGHtjXNabsMho= 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 Thu, Nov 20, 2025 at 10:12 AM Guopeng Zhang wr= ote: > > >On 11/19/25 20:27, Lance Yang wrote: >> From: Lance Yang >> >> >> On Wed, 19 Nov 2025 18:52:16 +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 syste= m >>> 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 uncharge= d. >>> >>> As a result, test_memcg_sock() can intermittently fail even though sock= et >>> memory accounting is working correctly. >>> >>> Make the test more robust by polling memory.stat for the "sock " counte= r >>> and allowing it some time to drop to zero instead of checking it only >>> once. 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. >Hi Lance, > >Thanks a lot for your review and helpful comments! >> >>Good catch! Thanks! >> >> With more CPU cores, updates may be distributed across cores, making it >> slower to reach the per-CPU flush threshold, IIUC :) >> >Yes, that matches what I=E2=80=99ve seen as well =E2=80=94 on larger syste= ms it indeed >takes longer for the stats to converge due to per-CPU distribution and >the flush threshold. Me too. I previously proposed a potential solution to explicitly flush stats via a new interface, "memory.stat_refresh" [1]. However, improving the existing flush mechanism would likely be a better long-term direction. Links: [1] https://lore.kernel.org/linux-mm/20251110101948.19277-1-leon.huangfu@sh= opee.com/ Thanks, Leon [...]