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Miller" , Vladimir Davydov , Kuniyuki Iwashima , linux-mm@kvack.org, Neal Cardwell Subject: Re: [PATCH] memcg: Keep socket_pressure fresh on 32-bit kernel. Message-Id: <20250716180232.6bcebe13e9a0d86019e1eaa0@linux-foundation.org> In-Reply-To: References: <20250716042925.106239-1-kuniyu@google.com> <20250716154315.b49d3af2cd9294faea24d6c2@linux-foundation.org> <20250716165220.4fe0019e7ecfcf73db13b334@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 46DD120009 X-Stat-Signature: 6wjn7cfpi8wtwd9mfhd9ziq6io1z8rzs X-HE-Tag: 1752714154-341653 X-HE-Meta: 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 BQi7SN2N uXbIPwVjJPieaKYnu+llWw8J9JfvjErvDabBNfdJA+eqrw0byzffQQXLbtCZdRHeZJEA188UQHkUEXrbIcygFJMkR6eTNbNqlTpBYXMPhVtH6N0iAOu8WOCSmU/Yqc6J4DGvh41lvHts/FlIluLEeG6ieSxSotqxMzLoo/QRQCXoJT7gNE3M5eZJyZLb6lkpOp0+KUPwkBBf5JGjFOqnBiuxgRbwIMGUfiVg2BnxbC0cMkVE3iqjFHFfPEHStSa2zMWp+NlVAytKXrBigVkciNwDQsLOROGqHvxkE3kNFC81+ndoK6bs/wBY4bY90OeYJ9vdswKANH2tUR9rx9FVhrehuUz9d6ZSbWr9PZlFCMVb3fKltr+TMxZINY73zpmY7YqUmn3CAZwGOAN87J1bBHW+BrbPKBUHHeE8t5/1rBdPVssYFviuB+inariregZ1Bv34WpOQtiJQR7aa1LSM4i5dc3MOB3RvrDH21 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 Wed, 16 Jul 2025 16:58:29 -0700 Kuniyuki Iwashima wrote: > On Wed, Jul 16, 2025 at 4:52 PM Andrew Morton wrote: > > > > On Wed, 16 Jul 2025 16:13:54 -0700 Kuniyuki Iwashima wrote: > > > > > > > Thus, we need to update socket_pressure to a recent timestamp > > > > > periodically on 32-bit kernel. > > > > > > > > > > Let's do that every 24 hours, with a variation of about 0 to 4 hours. > > > > > > > > Can't we simply convert ->socket_preesure to a 64-bit type? > > > > timespec64/time64_t/etc? > > > > > > I think it's doable with get_jiffies_64() & time_before64(). > > > > > > My thought was a delayed work would be better than adding > > > two seqlock in the networking fast path. > > > > Is it on a very fast path? mem_cgroup_under_socket_pressure() itself > > doesn't look very fastpath-friendly and seqcounts are fast. Bearing in > > mind that this affects 32-bit machines only. > > > > If a get_jiffies_64() call is demonstrated to be a performance issue > > then perhaps there's something sneaky we can do along the lines of > > reading jiffies_64 directly then falling back to get_jiffies_64() in > > the rare something-went-wrong path. Haven't thought about it :) > > > > Dunno, the proposed patch just feels like overkill for a silly > > 32/66-bit issue? > > Fair enough, I'll make it u64 in v2. > Well, please do pay attention to any performance impact. Measurements with some simple microbenchmark if possible?