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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vQBbT-00000000GWw-0WWk; Mon, 01 Dec 2025 21:38:39 +0000 Date: Mon, 1 Dec 2025 21:38:38 +0000 From: Matthew Wilcox To: Jaegeuk Kim Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mm@kvack.org Subject: Re: [PATCH 3/4] mm/readahead: add a_ops->ra_folio_order to get a desired folio order Message-ID: References: <20251201210152.909339-1-jaegeuk@kernel.org> <20251201210152.909339-4-jaegeuk@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam12 X-Rspam-User: X-Rspamd-Queue-Id: C3CCFC0010 X-Stat-Signature: w4ctirnrpzxx7tkwuukhy3jaafqksyga X-HE-Tag: 1764625120-696209 X-HE-Meta: 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 bymwbyZe cj+jOWJZogqu2K0v9RbrzPPFGtSlSthnhj49wI05MkeZuoROYm7S3xwDh/3SgI5jX9pvOhkwiAs21UjFlW8toL+4GV2G0uiJWGPCrnHg+uQ9cGTxY19SdtEq1LlAHJ9fuM2pVDjGelj+KO68NTPqeJTC9Op8Nbwv8HG2ZiTFe9qopghOwKQGTYIMqIUHMyIYp1J/S5njEoG6rVOYPGPwTETZnrsb1qp7viVz4V+ihYk/ULbHT+8HW2gdjBG92nWQRVx6vQrxNIt24JUQoei/hS5PdLNrE7YzP9AYpG6VRpbvNBLF0iE0BGxB39E6Si1AExq9r 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 Mon, Dec 01, 2025 at 09:24:41PM +0000, Jaegeuk Kim wrote: > On 12/01, Matthew Wilcox wrote: > > On Mon, Dec 01, 2025 at 09:01:26PM +0000, Jaegeuk Kim wrote: > > > This patch introduces a new address operation, a_ops->ra_folio_order(), which > > > proposes a new folio order based on the adjusted order for page_cache_sync_ra. > > > > > > Hence, each filesystem can set the desired minimum order of folio allocation > > > when requesting fadvise(POSIX_FADV_WILLNEED). > > > > Again, you've said what but not why. Does the mm code not ramp up the > > folio order sufficiently quickly? What are you trying to accomplish? > > That's why I posted a series of the patches to provide more details. Could you > please check the last patch in the series to show fadvise() does not increase > the folio order? > > https://lore.kernel.org/linux-f2fs-devel/20251201210152.909339-5-jaegeuk@kernel.org/T/#u So what you're trying to say is that readahead() currently only uses order-0 pages and you want it to use larger order pages? I agree with that! But I don't think this is the way to do it. We should just use larger order allocations, always. None of this "call the filesystem, check a sysfs parameter". Just use the largest order page that fits.