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Sun, 31 May 2026 00:12:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 57C321F00893; Sun, 31 May 2026 00:12:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780186329; bh=OYvRVj4ATb1VjPqyrKnbeBCWG0iaq3Bc8et+a/muwak=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=fHOhsAuR4ScpU7RKty78SP/q0nx98PvpFWPIMukzAHEP+/dxNLJI95BYxZOkZRH8b 0vvtGETBPj6snAsl5sZla2ANtjpOu4hsZ5T9xZfqKEMyFTJ+hOr94AJt2anvzGK+2I UUkR+VjHrS2bRTK7MRYAYRcbwjVawM7kdJGKgjfyVuHrHvzAsPTa4LYjInu5Z7qURl uNsap2grrmNTO60WkFlgwkIZCj4q1gkDfjY+QhvWLXJjz4UkmrfX7fYLTkcA4ucLZJ K8wxewMF4nOOu52EePN9R+PXM0YUBOJ2WgVAEF3VTJ1jlevVgFJhgTDaF6fDHUvvrK pcE0/tyMGqKtg== Date: Sun, 31 May 2026 00:12:07 +0000 To: Christoph Hellwig Message-ID: References: <20260522141115.GA8258@macsyma-wired.lan> <20260522224108.GA18663@macsyma-wired.lan> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Headers-End: 1wTTmu-000688-A4 Subject: Re: [f2fs-dev] [PATCH v2] f2fs: another way to set large folio by remembering inode number X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Jaegeuk Kim via Linux-f2fs-devel Reply-To: Jaegeuk Kim Cc: Theodore Tso , Bart Van Assche , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Matthew Wilcox , linux-f2fs-devel@lists.sourceforge.net, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Akilesh Kailash , Christian Brauner Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 05/28, Christoph Hellwig wrote: > On Wed, May 27, 2026 at 03:59:35PM +0000, Jaegeuk Kim wrote: > > F2FS merges bios before submit_bio, regardless of small or large folios, > > since the block addresses are consecutive. So, I think IO subsystem was > > working in full speed. > > As does every other remotely modern file system. But that merging is > surprisingly expensive, which is why using folios gets really major > performance improvements. > > For one doing these checks to merge touch quite a few cache lines. > Second, devices are often a lot more efficient if they see fewer SGL > entries. I.e. having a 1MB bio a single SGL tends to work better than > having 256 of them. > The same is true in the kernel code itself, both in the submission path > (dma mapping and co), and even more so in the page cache handling > both before submitting and in the completion path. > > See Bart's patch about how long the walk of the bio_vecs in the f2fs > completion path can take. We had similar issues in XFS even in the > workqueue completion path due to lack of rescheduling, and these simply > go away when you do the folio manipulation in larger chunks (LAZY_PREEMPT > would avoid the need to explicit rescheduling these days, but that just > papers over the symptoms in this case). > I see. That's also super helpful. Let me kick off the large folio support asap. Thanks. _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel