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Fri, 24 Jul 2026 03:22:11 -0700 (PDT) Message-ID: <2e61a4e1-20ed-4fe0-158c-5a9d060ce01a@gmail.com> Date: Fri, 24 Jul 2026 18:22:00 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.15.0 Subject: Re: [PATCH v2 0/2] mm/zswap: Fixes and improves the zswap global shrinker To: Yosry Ahmed Cc: Andrew Morton , nphamcs@gmail.com, tj@kernel.org, hannes@cmpxchg.org, shakeel.butt@linux.dev, mhocko@kernel.org, mkoutny@suse.com, chengming.zhou@linux.dev, muchun.song@linux.dev, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Hao Jia References: <20260717085151.22822-1-jiahao.kernel@gmail.com> <20260717181839.c94d0335ccef0084707d3d85@linux-foundation.org> <20260717214031.8b22e9a37ea3b0c564b466f0@linux-foundation.org> <7dbde343-fbbf-6a1d-1785-ebf9f5a04f6b@gmail.com> <0a96b7ec-0d8d-2abd-afaa-739c562bc985@gmail.com> From: Hao Jia In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: AC5AD4000A X-Stat-Signature: ts97iapnpj7wrgtxqh3ia9fzbaps5f7b X-HE-Tag: 1784888532-726037 X-HE-Meta: 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 afldR0uU 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026/7/23 12:49, Yosry Ahmed wrote: > On Wed, Jul 22, 2026 at 6:21 PM Hao Jia wrote: >> >> >> >> On 2026/7/20 09:26, Hao Jia wrote: >>> >>> >>> On 2026/7/18 12:40, Andrew Morton wrote: >>>> On Fri, 17 Jul 2026 18:28:04 -0700 Yosry Ahmed wrote: >>>> >>>>>> >>>>>> The [1/2] changelog lacks a description of how the flaw impacts users. >>>>>> Please describe this fully and maintain that info within the >>>>>> changelogging. This info helps -stable maintainers and others >>>>>> understand why we're proposing a backport and helps myself and others >>>>>> with timing decisions. >>>>> >>>>> The first line in the changelog should be sufficient imo: "Zswap >>>>> writeback on hitting the pool limit is broken when memory cgroup is >>>>> disabled" >>>> >>>> "broken"? Perhaps this means "fails to occur". >>>> >>>> But what is the userspace-visible impact? IOW, why are we proposing a >>>> backport? >>>> >>> >>> Perhaps the first paragraph of the commit1 message could be modified as >>> follows? I have added a description of the issues that occur without >>> this patch. >>> >> >> Hi Andrew, Yosry, and Nhat, >> Any thoughts on this change? > > I would front load the user impact in the first paragraph: > > Zswap writeback when the global pool limit is hit fails when memory > cgroups are disabled. The pool remains full until it is organically > drained by swapins or memory freeing, leading to zswap store failures > and pages bypassing getting written directly to the backing swap device, > causing LRU inversion (hotter pages with higher fault latency). > > ... Will done. Thanks, Hao