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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: <20250716165220.4fe0019e7ecfcf73db13b334@linux-foundation.org> In-Reply-To: References: <20250716042925.106239-1-kuniyu@google.com> <20250716154315.b49d3af2cd9294faea24d6c2@linux-foundation.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: 4uzheyah6cbznx47sfmehb1umbsyraar X-Rspam-User: X-Rspamd-Queue-Id: CDB2B120002 X-Rspamd-Server: rspam02 X-HE-Tag: 1752709942-640391 X-HE-Meta: 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 mhe7hT+w mvqLcbXb8Ce73XZCqUbGH+toIhXx/Jdo48BUoePCOB9YYaj0o+VPt5BQAhOH7qiTJe+pHjsucZhCtFbS9ESYhgZpXwBDARY0/Rhc++Sz8V2orqx8FpZgSC3mxoTB7QXBysI7ixs/RduCYGpfZh3i8MSxy98HdS0LTOueMhN7TAxHXXT0C3HEZgCoBk2gixziBmQszBINCCjGw8yJyt3LvIBjwCsHAel7yAProxdW62wxTcbWu3hoOD7XaK8gXMBb/5rwsar54axXPZlJLtio2r0ywGeFRLpeBLr2/Bc/pNDUIMi7m5pumoTN/cWb+bk1w6Pyst0cwmCWInGV+/xo7EAYGFG/YNeAlpgNeHxvmnaSor7DtihgQ7PuFU+On1gm9hCCO4WRkhAbOOnI= 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 16:13:54 -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?