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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1sFcyS-00000006PkX-3vg9; Fri, 07 Jun 2024 17:01:56 +0000 Date: Fri, 7 Jun 2024 18:01:56 +0100 From: Matthew Wilcox To: Zi Yan Cc: "Pankaj Raghav (Samsung)" , david@fromorbit.com, djwong@kernel.org, chandan.babu@oracle.com, brauner@kernel.org, akpm@linux-foundation.org, mcgrof@kernel.org, linux-mm@kvack.org, hare@suse.de, linux-kernel@vger.kernel.org, yang@os.amperecomputing.com, linux-xfs@vger.kernel.org, p.raghav@samsung.com, linux-fsdevel@vger.kernel.org, hch@lst.de, gost.dev@samsung.com, cl@os.amperecomputing.com, john.g.garry@oracle.com Subject: Re: [PATCH v7 05/11] mm: split a folio in minimum folio order chunks Message-ID: References: <20240607145902.1137853-1-kernel@pankajraghav.com> <20240607145902.1137853-6-kernel@pankajraghav.com> <75CCE180-EC90-4BDC-B5D8-0ED1B710BE49@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <75CCE180-EC90-4BDC-B5D8-0ED1B710BE49@nvidia.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 92D0D180014 X-Stat-Signature: oeu9ehhthoc8srjdiuqpdxngncggnpbq X-HE-Tag: 1717779726-32711 X-HE-Meta: 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 zFc2mqQr ZvLmPu0hkvTDiGEl6/2KGX97RkmtMUhxl6UBcKyHpphnioVhoM0VyOAcYvK6Wc77zRz05rzs5/dmlkyvy+FOiqLG24PC2tTeq3786Ji9ze9gWfD4Xe3DvhKpd0cXQiG3y5qc64IyT313v06g= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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, Jun 07, 2024 at 12:58:33PM -0400, Zi Yan wrote: > > +int split_folio_to_list(struct folio *folio, struct list_head *list) > > +{ > > + unsigned int min_order = 0; > > + > > + if (!folio_test_anon(folio)) { > > + if (!folio->mapping) { > > + count_vm_event(THP_SPLIT_PAGE_FAILED); > > You should only increase this counter when the input folio is a THP, namely > folio_test_pmd_mappable(folio) is true. For other large folios, we will > need a separate counter. Something like MTHP_STAT_FILE_SPLIT_FAILED. > See enum mthp_stat_item in include/linux/huge_mm.h. Also, why should this count as a split failure? If we see a NULL mapping, the folio has been truncated and so no longer needs to be split. I understand we currently count it as a failure, but I don't think we should.