From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: [PATCH 5/6] libext2fs/e2fsck: provide routines to read-ahead metadata Date: Mon, 11 Aug 2014 14:32:58 -0400 Message-ID: <20140811183258.GF6553@thunk.org> References: <20140809042610.2441.6868.stgit@birch.djwong.org> <20140809042643.2441.79312.stgit@birch.djwong.org> <20140811052151.GA2808@birch.djwong.org> <20140811062415.GG15431@thunk.org> <20140811063120.GB2808@birch.djwong.org> <20140811143423.GB3506@thunk.org> <20140811180509.GE2808@birch.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org To: "Darrick J. Wong" Return-path: Received: from imap.thunk.org ([74.207.234.97]:54983 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753506AbaHKSdA (ORCPT ); Mon, 11 Aug 2014 14:33:00 -0400 Content-Disposition: inline In-Reply-To: <20140811180509.GE2808@birch.djwong.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Aug 11, 2014 at 11:05:09AM -0700, Darrick J. Wong wrote: > > Using the bitmap turns out to be pretty quick (~130us to start RA for 4 groups > vs. ~70us per group if I issue the RA directly). Each fadvise call seems to > cost us ~1ms, so I'll keep using the bitmap to minimize the number of fadvise > calls, since it's also a lot less code. 4 groups? Since the default flex_bg size is 16 block groups, I would have expected that you would want to start RA every 16 groups. (And BTW, I've been wondering whether we should increase the flex_bg size for bigger file systems. By the time we get to 4TB disks, Having a flex_bg every 2GB seems a little small.) - Ted