From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from imap.thunk.org ([74.207.234.97]:51337 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751597AbaKYT0N (ORCPT ); Tue, 25 Nov 2014 14:26:13 -0500 Date: Tue, 25 Nov 2014 14:26:09 -0500 From: "Theodore Ts'o" To: Jan Kara Cc: Dave Chinner , linux-fsdevel@vger.kernel.org, Ext4 Developers List , linux-btrfs@vger.kernel.org, xfs@oss.sgi.com Subject: Re: [PATCH 2/4] vfs: add support for a lazytime mount option Message-ID: <20141125192609.GA28449@thunk.org> References: <1416599964-21892-1-git-send-email-tytso@mit.edu> <1416599964-21892-3-git-send-email-tytso@mit.edu> <20141125015239.GD27262@dastard> <20141125043335.GF31339@thunk.org> <20141125173040.GD3228@quack.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20141125173040.GD3228@quack.suse.cz> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Tue, Nov 25, 2014 at 06:30:40PM +0100, Jan Kara wrote: > This would be possible and as Boaz says, it might be possible to reuse > the same list_head in the inode for this. Getting rid of the full scan of > all superblock inodes would be nice (as the scan gets really expensive for > large numbers of inodes (think of i_sb_lock contention) and this makes it > twice as bad) so I'd prefer to do this if possible. Fair enough, I'll give this a try. Personally, I've never been that solicitous towards the efficiency of sync, since if you ever use it, you tend to destroy performance just because of contention of the disk drive head caused by the writeback, never mind the i_sb_lock contention. ("I am sync(2), the destroyer of tail latency SLO's...") In fact there has sometimes been discussion about disabling sync(2) from non-root users, because the opportunity for mischief when a developer logs and types sync out of reflex is too high. Of course, if we ever did this, I'm sure such a patch would never be accepted upstream, but that's OK, most people don't seem to care about tail latency outside of Facebook and Google anyway.... - Ted