From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6C97F3655E8; Wed, 27 May 2026 06:28:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779863316; cv=none; b=UTdHQZ4XfxnJIW8DnB4OkCR7on9CxoZg9skwt+0UEZnYtyPpvkMOP0jun7cES8D4X2czMIGXrTsh/Qyfspik6ua7qNbgpHHQI/tDth1YMYA61FAB2ZJx50W5PI1bjmwrYqxDynmqE/Jg1YBxiZkpB8E/JLknK/msLJW6QYcOI7k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779863316; c=relaxed/simple; bh=RLrZ6IfmbbJO06SvlF07nmPcHuhdw0xUgD0X1837g48=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=m2ebtxCsS3u7U51DsyCPw8VkUJMQ3n897SHrQOQlDT925YoGl6+7bN+XjXDsI67AdxaW+gz1FPfeE7j3jUuYKj+7TQAeHyzkK6G9nIYkFb/mq2oIpy7AewdmaYbjyXrANXclFgNJx/XkN+93YJuhiWFqOiL5vxFnB4Q2IfbayIk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=nS7j8vx2; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="nS7j8vx2" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Ka/9L3mGRr/AbgLqT0X1N/LKODg56XkQXKLxkU0UHzU=; b=nS7j8vx2eymE0ZSZoDXuT2yyfB /S4PFwuANnKUoJp7Giy3+PPZL2gSAx1o/0tYaYdwpEB5m5NxnKmi0la7rA+Kdjp8Tg0DTzC3wbrdb p0SdCWxYoxDL4R+uCloO+ntIkscwqjOUheJxRyg6k3URoBMbJg02NwWXHUDRHOhOsoUcznSjqCr7R nzTIsYlAv+FvrDCQTadRi0C0ba3pnNgQPJvhBxUeWgi03KEwJcO3vfxYgKtesqiYn6VhwjAlat7Im ccYCea5H39rArdAXYTH8KgLSGMAdaGm9wmifOC0WrWvLVA7yRspaKDM4ho8hHu1TqWsRqsxOjMKHA XhyVjWPw==; Received: from hch by bombadil.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1wS7ki-00000003Ozf-3Lht; Wed, 27 May 2026 06:28:28 +0000 Date: Tue, 26 May 2026 23:28:28 -0700 From: Christoph Hellwig To: Bart Van Assche Cc: Theodore Tso , Jaegeuk Kim , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Matthew Wilcox , linux-f2fs-devel@lists.sourceforge.net, Christoph Hellwig , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Akilesh Kailash , Christian Brauner Subject: Re: [f2fs-dev] [PATCH v2] f2fs: another way to set large folio by remembering inode number Message-ID: References: <20260521155748.GA79343@macsyma-wired.lan> <20260522141115.GA8258@macsyma-wired.lan> <20260522224108.GA18663@macsyma-wired.lan> Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, May 26, 2026 at 09:14:52AM -0700, Bart Van Assche wrote: > On 5/26/26 6:42 AM, Theodore Tso wrote: > > It seems... surprising that the additional I/O operations are actually > > throttloing UFS device bandwidth by 2x (4GB/s vs 2GB/s). Have you dug > > into why this is happening, and whether there is anything that can be > > optimized below the file system? > The layers below the filesystem (block, SCSI, UFS) is what I'm > responsible for in the Pixel team and I can assure you that these are > highly optimized. > > Since the transfer size used in Jaegeuk's tests is much larger than 4 > KiB, how many CPU cycles are used per IO by the layers below the > filesystem is not limiting the transfer bandwidth. I'm honestly not sure what discussion we have here. Larger I/O is pretty much always more efficient. If you submit smaller I/O you need more merging to build it back up larger, and more I/Os. Which is exaxtly why we need large folio support everywhere, as it makes a huge difference in I/O performance.