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Fri, 07 Mar 2025 15:03:45 -0800 (PST) MIME-Version: 1.0 References: <20250307120141.1566673-1-qun-wei.lin@mediatek.com> In-Reply-To: <20250307120141.1566673-1-qun-wei.lin@mediatek.com> From: Nhat Pham Date: Fri, 7 Mar 2025 15:03:34 -0800 X-Gm-Features: AQ5f1Jr_FBnz9qk1uNlckq4_7pHKTqldI029tYPnmq326QX8Uckh0mZErYX0PQo Message-ID: Subject: Re: [PATCH 0/2] Improve Zram by separating compression context from kswapd To: Qun-Wei Lin Cc: Jens Axboe , Minchan Kim , Sergey Senozhatsky , Vishal Verma , Dan Williams , Dave Jiang , Ira Weiny , Andrew Morton , Matthias Brugger , AngeloGioacchino Del Regno , Chris Li , Ryan Roberts , "Huang, Ying" , Kairui Song , Dan Schatzberg , Barry Song , Al Viro , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, nvdimm@lists.linux.dev, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, Casper Li , Chinwen Chang , Andrew Yang , James Hsu Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: C92D540018 X-Stat-Signature: 44kqg1yu4b4rhmmoniqdok7ar8sqw734 X-Rspam-User: X-HE-Tag: 1741388626-292087 X-HE-Meta: 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 ab+sKcsX mVF3juj/d/dwXJbsHKB2j7FlqDBCvH8U4tJ/xoGoV7yP5+0lQ/QafmfewuxZf6Mnu5O/TQEes0f/e6V+l3LI7rJayfOx/WFJSXNCmFXwA6dr2oCFy/Pdid12QeLAae5q+NIn7mQzLOcn7ZSkwAXRCAhDzeat8kFcIU83tqUS6neGkvQUnN01PxC3mcRUgGB5bGjcoYWMSTAjn00g8OfsEKQSCYZh0RTflUiTEIkEo5KVjWVeH84k8zzkhjoBDiUCPO7XQXDzG7tm6K8M6clYXTYtzSE6YMHQtenieyjkYvUPZYV/UAsNM08WCtDWyy0rB1tM5+R3BSkRjennkx8yNBqgpc2BZYZ728S5VV44WHfuLL/sUHI1B3lbWpNbWoGVvv+6jM+Ex5LybOaa+NpTBHR1NXc8IkVMh+Ddx X-Bogosity: Ham, tests=bogofilter, spamicity=0.000036, 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 Fri, Mar 7, 2025 at 4:02=E2=80=AFAM Qun-Wei Lin wrote: > > This patch series introduces a new mechanism called kcompressd to > improve the efficiency of memory reclaiming in the operating system. The > main goal is to separate the tasks of page scanning and page compression > into distinct processes or threads, thereby reducing the load on the > kswapd thread and enhancing overall system performance under high memory > pressure conditions. Please excuse my ignorance, but from your cover letter I still don't quite get what is the problem here? And how would decouple compression and scanning help? > > Problem: > In the current system, the kswapd thread is responsible for both > scanning the LRU pages and compressing pages into the ZRAM. This > combined responsibility can lead to significant performance bottlenecks, What bottleneck are we talking about? Is one stage slower than the other? > especially under high memory pressure. The kswapd thread becomes a > single point of contention, causing delays in memory reclaiming and > overall system performance degradation. > > Target: > The target of this invention is to improve the efficiency of memory > reclaiming. By separating the tasks of page scanning and page > compression into distinct processes or threads, the system can handle > memory pressure more effectively. I'm not a zram maintainer, so I'm definitely not trying to stop this patch. But whatever problem zram is facing will likely occur with zswap too, so I'd like to learn more :)