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Fri, 26 Jun 2026 02:39:57 -0700 (PDT) Received: from localhost ([2603:7001:f100:500:365a:60ff:fe62:ff29]) by smtp.gmail.com with ESMTPSA id af79cd13be357-925fd391b22sm1107164385a.2.2026.06.26.02.39.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jun 2026 02:39:56 -0700 (PDT) Date: Fri, 26 Jun 2026 05:39:56 -0400 From: Johannes Weiner To: Qi Zheng Cc: Harry Yoo , akpm@linux-foundation.org, david@kernel.org, kasong@tencent.com, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, muchun.song@linux.dev, peiyang_he@smail.nju.edu.cn, mhocko@kernel.org, roman.gushchin@linux.dev, ljs@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qi Zheng , stable@vger.kernel.org Subject: Re: [PATCH v3] mm: mglru: fix stale batch updates after memcg reparenting Message-ID: References: <20260625151554.55105-1-qi.zheng@linux.dev> <4c7b0c46-14f0-4a62-893e-e50714e09b74@linux.dev> <46ac28bf-5be1-4600-b522-0a1aa76c28e6@kernel.org> <08cf8972-6cfc-4452-9a3c-88e0368dbbf9@linux.dev> <90fd5300-1016-42e7-abad-08ad85fb62b4@linux.dev> <5a0c6597-6b96-4781-a71b-fd1298b2b7bb@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 9p3anr5amiferqy8fhb5w1edyfbaqncq X-Rspam-User: X-Rspamd-Queue-Id: 99E17140002 X-Rspamd-Server: rspam02 X-HE-Tag: 1782466798-512239 X-HE-Meta: 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 oZtnaj3M XgcGn/dreaAfdvl1T8u1/sfEA52dP0Ffaj/H9v4h+ypqRsBTUCQG5UegcFqLlEfXZK24WkVfkqx+Ga+4N6+jzSCvvPB/MH4MgJejeTADgyklTPftO0c/LWIzARN5jTDV2RB6b+UEHmdPkkDtj5Qu67uIpb12nb0EeBzwEGyv68kfat/E1Yi/tTPsbexmGwQ+dcyJcJEdX28d9CK13xv9MaswQxUX7XoTlnjv0L+rrmel0TD4V889QCnEWUFqruF5tsiGF1OrcD/mNbXymYidP5K2acIr15eRYOn+toysYlmvEedoMS252JN7u39IgWlDciN1mzbpaXs/UMnadKmL6HI5HwMOeDFlRAk4Y5osIUibcZWV4epJ2MYqJWtGIUPfIRsOB3hFYtjxU8znRfst6DeWWAQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jun 26, 2026 at 03:04:17PM +0800, Qi Zheng wrote: > On 6/26/26 2:48 PM, Harry Yoo wrote: > > On 6/26/26 3:24 PM, Qi Zheng wrote: > >> On 6/26/26 12:59 PM, Harry Yoo wrote: > >>> Observing a dying cgroup should be rare anyway, it's worth focusing > >>> more on readability? > >> > >> While it's rare to encounter consecutive dying memcgs, it can still > >> happen, right? > > > > But is worth saving a few instruction in a basic block that is > > unlikely() to be executed? > > I don't have a strong opinion here. Hi Johannes, I'll leave the decision > up to you. If necessary, I can send out the v4. Yes, I was thinking what Harry actually bothered to spell out ;) The race is rare, multiple levels even rarer, and even *then* mem_cgroup_lruvec() is a quick inline. This way you have one block to handle that one rare race condition. One place to put the comment. No labels, no goto. Simplicity wins :)