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charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 093EF180011 X-Stat-Signature: ufp17cpianxbb8dn1wqttujstocj686z X-HE-Tag: 1694460857-794472 X-HE-Meta: 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 i4hsJd2L hiEsff0Y8Iv03HYo/toznuHfS3o9pzQgb+B+xqrlOOxRUJ697zAJMDmLI98FwbYPezgVF+LB9bxZ3OmSVcFlvplWqXpkB/rM/Pmbs/JwkrYx9Z2tocZLMRdjIFQVkFWpbZkP7YQTUuRy2TyXazTrvw4GoMG8BOZvnRMI4zn9Elst0zpdPLzse5jePnBdHhHSnG11gbkHRIvSwMTE= 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: On Mon 11-09-23 12:15:24, Wei Xu wrote: > On Mon, Sep 11, 2023 at 6:11 AM Michal Hocko wrote: > > > > On Thu 07-09-23 17:52:12, Wei Xu wrote: > > [...] > > > I tested this patch on a machine with 384 CPUs using a microbenchmark > > > that spawns 10K threads, each reading its memory.stat every 100 > > > milliseconds. > > > > This is rather extreme case but I wouldn't call it utterly insane > > though. > > > > > Most of memory.stat reads take 5ms-10ms in kernel, with > > > ~5% reads even exceeding 1 second. > > > > Just curious, what would numbers look like if the mutex is removed and > > those threads would be condending on the existing spinlock with lock > > dropping in place and removed. Would you be willing to give it a shot? > > Without the mutex and with the spinlock only, the common read latency > of memory.stat is still 5ms-10ms in kernel. There are very few reads > (<0.003%) going above 10ms and none more than 1 second. Is this with the existing spinlock dropping and same 10k potentially contending readers? -- Michal Hocko SUSE Labs