Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755243AbZCYUny (ORCPT ); Wed, 25 Mar 2009 16:43:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752337AbZCYUnp (ORCPT ); Wed, 25 Mar 2009 16:43:45 -0400 Received: from extu-mxob-1.symantec.com ([216.10.194.28]:50577 "EHLO extu-mxob-1.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752098AbZCYUno (ORCPT ); Wed, 25 Mar 2009 16:43:44 -0400 Date: Wed, 25 Mar 2009 20:41:17 +0000 (GMT) From: Hugh Dickins X-X-Sender: hugh@blonde.anvils To: Jens Axboe cc: Ric Wheeler , Jeff Garzik , Linus Torvalds , Theodore Tso , Ingo Molnar , Alan Cox , Arjan van de Ven , Andrew Morton , Peter Zijlstra , Nick Piggin , David Rees , Jesper Krogh , Linux Kernel Mailing List Subject: Re: Linux 2.6.29 In-Reply-To: <20090325195747.GC27476@kernel.dk> Message-ID: References: <20090324103111.GA26691@elte.hu> <20090324132032.GK5814@mit.edu> <20090324184549.GE32307@mit.edu> <49C93AB0.6070300@garzik.org> <20090325093913.GJ27476@kernel.dk> <49CA86BD.6060205@garzik.org> <20090325194341.GB27476@kernel.dk> <49CA8ADA.3040709@redhat.com> <20090325195747.GC27476@kernel.dk> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1348 Lines: 30 On Wed, 25 Mar 2009, Jens Axboe wrote: > On Wed, Mar 25 2009, Ric Wheeler wrote: > > Jens Axboe wrote: > >> > >> Another problem is that FLUSH_CACHE sucks. Really. And not just on > >> ext3/ordered, generally. Write a 50 byte file, fsync, flush cache and > >> wit for the world to finish. Pretty hard to teach people to use a nicer > >> fdatasync(), when the majority of the cost now becomes flushing the > >> cache of that 1TB drive you happen to have 8 partitions on. Good luck > >> with that. > >> > > And, as I am sure that you do know, to add insult to injury, FLUSH_CACHE > > is per device (not file system). > > > > When you issue an fsync() on a disk with multiple partitions, you will > > flush the data for all of its partitions from the write cache.... > > Exactly, that's what my (vague) 8 partition reference was for :-) > A range flush would be so much more palatable. Tangential question, but am I right in thinking that BIO_RW_BARRIER similarly bars across all partitions, whereas its WRITE_BARRIER and DISCARD_BARRIER users would actually prefer it to apply to just one? Hugh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/