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Mercier" Cc: Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Efly Young , android-mm@google.com, yuzhao@google.com, mkoutny@suse.com, Yosry Ahmed , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm: memcg: Use larger batches for proactive reclaim Message-ID: References: <20240202233855.1236422-1-tjmercier@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: EE5D5100003 X-Stat-Signature: ayrpcfz98m584jyqmgcfksjz3wfymrqq X-Rspam-User: X-HE-Tag: 1707209922-910441 X-HE-Meta: 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 sLVmlamS eI5/mqEGpkhLb4jWLKvPBobafehA9VkDMAiAf/W4JktW/kqFd7QWLw/10wHClBdEmmPFAsOKYcCIUNoDKCv2a2m9aNcKQ7CH1XnpNeGL3pU3FTZsG6UvXvfY+9W8/9N/FDVjt2RgUgWeT18nxS0zXR02392d/FVl+BLCDd0OlwwT05l8wzvZ41moXpiixcRxPlvwzbDzFasDJv2rxlkdhEi51MVIjTnID4xGMaAvt6zRtTza3a+M5kodO/Cbp9tqwax0KARAs9YQvu4JWHD9yui/jM146YXMpTZ8qIQ4Go8G3WCs= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, 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 05-02-24 20:01:40, T.J. Mercier wrote: > On Mon, Feb 5, 2024 at 1:16 PM Michal Hocko wrote: > > > > On Mon 05-02-24 12:47:47, T.J. Mercier wrote: > > > On Mon, Feb 5, 2024 at 12:36 PM Michal Hocko wrote: > > [...] > > > > This of something like > > > > timeout $TIMEOUT echo $TARGET > $MEMCG_PATH/memory.reclaim > > > > where timeout acts as a stop gap if the reclaim cannot finish in > > > > TIMEOUT. > > > > > > Yeah I get the desired behavior, but using sc->nr_reclaimed to achieve > > > it is what's bothering me. > > > > I am not really happy about this subtlety. If we have a better way then > > let's do it. Better in its own patch, though. > > > > > It's already wired up that way though, so if you want to make this > > > change now then I can try to test for the difference using really > > > large reclaim targets. > > > > Yes, please. If you want it a separate patch then no objection from me > > of course. If you do no like the nr_to_reclaim bailout then maybe we can > > go with a simple break out flag in scan_control. > > > > Thanks! > > It's a bit difficult to test under the too_many_isolated check, so I > moved the fatal_signal_pending check outside and tried with that. > Performing full reclaim on the /uid_0 cgroup with a 250ms delay before > SIGKILL, I got an average of 16ms better latency with > sc->nr_to_reclaim across 20 runs ignoring one 1s outlier with > SWAP_CLUSTER_MAX. This will obviously scale with the number of memcgs in the hierarchy but you are right that too_many_isolated makes the whole fatal_signal_pending check rather inefficient. I haven't missed that. The reclaim path is rather convoluted so this will likely be more complex than I anticipated. I will think about that some more. In order to not delay your patch, please repost with suggested updates to the changelog. This needs addressing IMO but I do not think this is critical at this stage. -- Michal Hocko SUSE Labs