From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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.lore.kernel.org (Postfix) with ESMTPS id 4C538C47DDB for ; Tue, 23 Jan 2024 08:40:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=CXkIY3wk7h71lKOG+iKPfCtgskVq40Hz3IMYfFS6bQE=; b=y88llkvrrkYzZZDZz5uzuIop2+ 5rPObfWFSXCLmPBZBgpFz+QxQm7u5D3yrrVG8ReQekuiiCgg7ZA89jZ7ah6kK7QM4LzOzzc3sHKyl CbycsW2lUrD311JPuRG+yzACmv4zCZXYfOWdgoK0/GrHtSSjJ8rhyzUjKNHmiWOHeA+p+iAwyxXnZ 9hJP2Mc3CtcJWEutYhIRDGQC1pu/RDqaaWFvbb7NsudtbsrzLruUagvU4peBKHTx7xrbEZOr88as/ GMEZ0ZCYdwJ21AAciz2QT8lkdptiWvHde4x2n+Nt89Ez3mVC4iRh/Jv/ef08sj28K8r4a7DFgeCix LXhuLUjg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rSCKj-00Fbe3-2k; Tue, 23 Jan 2024 08:40:37 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1rSCKh-00FbdC-0n for linux-nvme@lists.infradead.org; Tue, 23 Jan 2024 08:40:36 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 716F968BEB; Tue, 23 Jan 2024 09:40:29 +0100 (CET) Date: Tue, 23 Jan 2024 09:40:29 +0100 From: Christoph Hellwig To: Damien Le Moal Cc: Christoph Hellwig , Jens Axboe , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , Paolo Bonzini , Stefan Hajnoczi , "Martin K. Petersen" , Keith Busch , Sagi Grimberg , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, virtualization@lists.linux.dev Subject: Re: [PATCH 02/15] block: refactor disk_update_readahead Message-ID: <20240123084029.GA29041@lst.de> References: <20240122173645.1686078-1-hch@lst.de> <20240122173645.1686078-3-hch@lst.de> <96007133-162c-4fff-9343-dd88ca520aa7@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <96007133-162c-4fff-9343-dd88ca520aa7@kernel.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240123_004035_427933_87BB742D X-CRM114-Status: GOOD ( 14.53 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Tue, Jan 23, 2024 at 01:41:05PM +0900, Damien Le Moal wrote: > > +{ > > + /* > > + * For read-ahead of large files to be effective, we need to read ahead > > + * at least twice the optimal I/O size. > > + */ > > + bdi->ra_pages = max(lim->io_opt * 2 / PAGE_SIZE, VM_READAHEAD_PAGES); > > Nit: while at it, you could replace that division by PAGE_SIZE with a right > shift by PAGE_SHIFT. I don't really see the point, this is everything but a fast path, and for simple constant divisions compilers aren't actually bad at doing optimizations.