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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6d1798b764bsm41775366d6.44.2024.10.29.06.14.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Oct 2024 06:14:25 -0700 (PDT) Date: Tue, 29 Oct 2024 09:14:31 -0400 From: Gregory Price To: "Huang, Ying" Cc: Yang Shi , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com, akpm@linux-foundation.org, weixugc@google.com, dave.hansen@linux.intel.com, osalvador@suse.de, stable@vger.kernel.org Subject: Re: [PATCH] vmscan,migrate: fix double-decrement on node stats when demoting pages Message-ID: References: <20241025141724.17927-1-gourry@gourry.net> <87msinwxut.fsf@yhuang6-desk2.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87msinwxut.fsf@yhuang6-desk2.ccr.corp.intel.com> X-Stat-Signature: r1n7k3easyf8fm633sw83gk9y8swffa9 X-Rspamd-Queue-Id: 3F63BA0022 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1730207650-413266 X-HE-Meta: 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 1ZW870CW +gAfYcJ4sfQJIGuEWd8AYS/MbpYh48gZj70D+c+aqnEyZFnCSkpIlYMutdLp/UQUsewL5UNLaH87dtoO26J6GiIOGm/4IzWg3va272sxcZ8QBY5jmRCVz4EbStqfnq528lxffQIPJUhFmnskFnMhti8Q5ZGXYGEyUyss+bvBYzDumflaXhnV8kGuznlvvJyUtbqcSieof6P25t3yNtEjvkNYqrGunwQNANTLmjCjrWZGOq/uR13f7OxITlC1ie9v/1PInS5ajhdAmkBAqhsHat0ZJEwzwC1eanJERXAekdrlziu2LTqZtl6mcl9q883hjicCv4DSCovx90w7dXautMvSygzYy1rj0JygWhhLYvyshNo2lXbtOxxx4+w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.001955, 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 Tue, Oct 29, 2024 at 08:34:34AM +0800, Huang, Ying wrote: > Gregory Price writes: > > > On Mon, Oct 28, 2024 at 01:45:48PM -0700, Yang Shi wrote: > >> On Fri, Oct 25, 2024 at 7:17 AM Gregory Price wrote: > >> > > >> > This path happens for SUCCESSFUL migrations, not failures. Typically > >> > callers to migrate_pages are required to handle putback/accounting for > >> > failures, but this is already handled in the shrink code. > >> > >> AFAIK, MGLRU doesn't dec/inc this counter, so it is not > >> double-decrement for MGLRU. Maybe "imbalance update" is better? > >> Anyway, it is just a nit. I'd suggest capturing the MGLRU case in the > >> commit log too. > >> > > > > Gotcha, so yeah saying it's an imbalance fix is more accurate. > > > > So more accurate changelog is: ... > > I think that it may be better to mention the different behavior of LRU > and MGLRU. But that's not a big deal, change it again only if you think > it's necessary. > The behavior isn't really different. It's either way migrate_pages decrements when it shouldn't going through the shink code - and both LRU and MGLRU go through the same code. That LRU does an inc/dec pair is irrelevant - neither should do the decrement in the migrate path. ~Gregory