From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [PATCH 0/2 RFC v3] Livelock avoidance for data integrity writeback Date: Sun, 6 Jun 2010 17:52:58 +1000 Message-ID: <20100606075258.GK26335@laptop> References: <1275677231-15662-1-git-send-email-jack@suse.cz> <20100605011447.GF26335@laptop> <20100606040819.GA16293@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , linux-fsdevel@vger.kernel.org, Andrew Morton , david@fromorbit.com, linux-mm@kvack.org To: Wu Fengguang Return-path: Received: from cantor.suse.de ([195.135.220.2]:50447 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752227Ab0FFHxG (ORCPT ); Sun, 6 Jun 2010 03:53:06 -0400 Content-Disposition: inline In-Reply-To: <20100606040819.GA16293@localhost> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Sun, Jun 06, 2010 at 12:08:19PM +0800, Wu Fengguang wrote: > On Sat, Jun 05, 2010 at 11:14:47AM +1000, Nick Piggin wrote: > > On Fri, Jun 04, 2010 at 08:47:09PM +0200, Jan Kara wrote: > > > > > > Hi, > > > > > > I've revived my patches to implement livelock avoidance for data integrity > > > writes. Due to some concerns whether tagging of pages before writeout cannot > > > be too costly to use for WB_SYNC_NONE mode (where we stop after nr_to_write > > > pages) I've changed the patch to use page tagging only in WB_SYNC_ALL mode > > > where we are sure that we write out all the tagged pages. Later, we can think > > > about using tagging for livelock avoidance for WB_SYNC_NONE mode as well... > > > > Hmm what concerns? Do you have any numbers? > > sync() is performed in two stages: the WB_SYNC_NONE run and the > WB_SYNC_ALL run. The WB_SYNC_NONE stage can still be livelocked. By concerns, I mean Jan's _performance_ concerns. I would prefer to minimise them, and then try to get an idea of the performance impact of doing tagging unconditionally.