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t=1781199558; bh=EDVNXhL2Pfk2NWjHVmUzJTm6IqAYDANPcobDFgmKGWg=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=BHbkmLxC9oZUeSXsvuN7EeETvKhppZNCiJLffMi5U8/+iNueDNzhoRtOta14y3//J si5BbetblwiOz15awvoRP9Q0yltQG9G4PJ0ow1o29o1wuxWPQQh8Xn0cMwpVmEfkGQ 1ImvBKSBZ7yIN7KNE9CGBNku0v4iZEjDtovmr7034CX8KGq+wWpKT5LyXiOreR7CWD DXhq+ZhzvjFsXdY8P08EpFWi3ZmjZSz15DX/bwmLQVlv1rbYnQQ05uCgwnSisfgWnv ZCfVo9utox81XMowyQqzQUOKl+KTB9gHzbYRj0UmHvXBI1s6FNwNUwyCXw87KcBLn8 oxsgp/LWYbXFQ== Date: Thu, 11 Jun 2026 17:39:16 +0000 From: Yosry Ahmed To: Hao Jia Cc: Nhat Pham , shakeel.butt@linux.dev, akpm@linux-foundation.org, tj@kernel.org, hannes@cmpxchg.org, mhocko@kernel.org, mkoutny@suse.com, chengming.zhou@linux.dev, muchun.song@linux.dev, roman.gushchin@linux.dev, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Hao Jia Subject: Re: [PATCH v3 1/4] mm/zswap: Make shrink_worker writeback cursor per-memcg Message-ID: References: <9898f83d-fae9-e284-6b85-c7f4089840a0@gmail.com> <90730fa7-62e7-d5f4-b638-23b22a8509f2@gmail.com> <1c25650e-bf98-2863-d505-9b94c385668b@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1c25650e-bf98-2863-d505-9b94c385668b@gmail.com> X-Rspamd-Queue-Id: 1AFCE4000F X-Stat-Signature: eb11wnwqfzw15rn563uht9ckuyraoqqy X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1781199559-781120 X-HE-Meta: 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 Mbvjbs5G 9KRDMLnzPG8MpaCh/ZzduC2XndrLmYOFfZD7ztb6eQlPaWVVjkh0TCqqoWn5885EQq/oTrqK8SZl9qenQ0G/VKDw7m1ZuZzZ11yDqut2qBIw5ZmQPU26M8XhbBo6kut1xUqhb/WCN116KsNzYIrbYzw0yAsx8st3S3UuoZPZipudx4Wus3rcD+b68Ip6IpLdi2IeQVEBLDMwADQ8SxJ27RvBRX9rwuny46qCooKH+4q4Y4MNJ9f55Vile31hPUmr1WmTWUl15WdK0XWbkTgF2q2aeFCtIDFKwUDTJqZVqx+f3lCuQSVV1RnpkuFTf7lewmViraRNRh53l+dZBRYaoSAFVujmTPmn4GvT+90JwyqRoQSZaa1RVDo6Ytq3y2FMyoeo83QDE9yhoP2feuiNB6jGXoUvhxC6zDGFVkCXinZZMhR0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jun 09, 2026 at 11:18:26AM +0800, Hao Jia wrote: > > > On 2026/6/9 02:01, Nhat Pham wrote: > > On Mon, Jun 8, 2026 at 9:48 AM Yosry Ahmed wrote: > > > > > > > But OTOH, this does seem like a recipe for inefficient reclaim. We > > > > might exhaust hotter memory of a cgroup while sparing colder memory of > > > > another cgroup... But maybe if they're all cold anyway, then who > > > > cares, and eventually you'll get to the cold stuff of other child? > > > > > > Forgot to respond to this part, the unfairness is limited to the batch > > > size per-invocation, so it should be fine as long as you don't divide > > > the amount over 100 iterations for some reason. Also yes, all memory > > > in zswap is cold, the relative coldness is not that important (e.g. > > > compared to relative coldness during reclaim). > > > > Ok then yeah, I think we should shelve per-memcg cursor for the next > > version. Down the line, if we have more data that unfairness is an > > issue, we can always fix it. One step at a time :) > > Thanks a lot to Yosry, Nhat, and Shakeel for the great suggestions! > > Let me summarize what I plan to do in the next version to make sure we are > on the same page: > > - Drop the per-memcg cursor and keep the root cgroup cursor > (zswap_next_shrink) logic intact. > - Stick to using the zswap_writeback_only key, and change the proactive > writeback size to use the compressed size. > - Consolidate and reuse the logic between shrink_worker() and > shrink_memcg(). Enable batch writeback in the shrink_worker() path, while > keeping the writeback behavior in the zswap_store() path unchanged. > > Please let me know if I missed or misunderstood anything. Thanks again for > clearing things up! Sorry for the late response, yes I think this makes sense. However, I have some comment about how this interacts with swap tiering, let me reply to the other thread. > > Thanks， > Hao