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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qG93z-007pby-VW; Mon, 03 Jul 2023 02:13:16 +0000 Date: Mon, 3 Jul 2023 03:13:15 +0100 From: Matthew Wilcox To: Andrew Morton Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jan Kara , Christoph Hellwig Subject: Re: [PATCH] writeback: Account the number of pages written back Message-ID: References: <20230628185548.981888-1-willy@infradead.org> <20230702130615.b72616d7f03b3ab4f6fc8dab@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230702130615.b72616d7f03b3ab4f6fc8dab@linux-foundation.org> X-Rspamd-Queue-Id: 7EF39140009 X-Rspam-User: X-Stat-Signature: czt973qa75ca6q53wd6p6ncoe3zn87dt X-Rspamd-Server: rspam01 X-HE-Tag: 1688350402-637361 X-HE-Meta: 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 ulK3jofD iGg6c1OtwmcCqdhNLdL+o3Z3churnUadUlVo+dOSpBiOXYIkKm6Y0iMNz9d4T2o32io8andq585LZN40JySF/vJ84ajDX36TUpSMON+fiBh6K8onjQmxEue+MaiCLFwOCzPoYIa3PEKYbQlV1/SH5Lg96goL3Rj6WKQqMMjKm8z+Js6PIhPaK+MVPhZnpsvz1tu9FemkDB1eezDnMDjDK9LejvmvBBOv6MtM1 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: On Sun, Jul 02, 2023 at 01:06:15PM -0700, Andrew Morton wrote: > On Wed, 28 Jun 2023 19:55:48 +0100 "Matthew Wilcox (Oracle)" wrote: > > > nr_to_write is a count of pages, so we need to decrease it by the number > > of pages in the folio we just wrote, not by 1. Most callers specify > > either LONG_MAX or 1, so are unaffected, but writeback_sb_inodes() > > might end up writing 512x as many pages as it asked for. > > 512 is a big number, Should we backport this? I'm really not sure. Maybe? I'm hoping one of the bots comes up with a meaningful performance change as a result of this patch and we find out. > > Fixes: 793917d997df ("mm/readahead: Add large folio readahead") > > I'm not seeing how a readahead change messed up writeback accounting? That was the first patch which allowed large folios to be added to the page cache. Until that point, this was latent. We could probably argue for one of a dozen other commits around the same time.