From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 23F6E6B004A for ; Wed, 17 Nov 2010 19:53:28 -0500 (EST) Date: Wed, 17 Nov 2010 16:53:09 -0800 From: Andrew Morton Subject: Re: [PATCH 3/3] mlock: avoid dirtying pages and triggering writeback Message-Id: <20101117165309.fa859fd3.akpm@linux-foundation.org> In-Reply-To: <20101117235230.GL3290@thunk.org> References: <1289996638-21439-1-git-send-email-walken@google.com> <1289996638-21439-4-git-send-email-walken@google.com> <20101117125756.GA5576@amd> <1290007734.2109.941.camel@laptop> <20101117231143.GQ22876@dastard> <20101117235230.GL3290@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Ted Ts'o Cc: Dave Chinner , Michel Lespinasse , Peter Zijlstra , Nick Piggin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Rik van Riel , Kosaki Motohiro , Theodore Tso , Michael Rubin , Suleiman Souhlal List-ID: On Wed, 17 Nov 2010 18:52:30 -0500 "Ted Ts'o" wrote: > On Thu, Nov 18, 2010 at 10:11:43AM +1100, Dave Chinner wrote: > > I don't think ->page_mkwrite can be worked around - we need that to > > be called on the first write fault of any mmap()d page to ensure it > > is set up correctly for writeback. If we don't get write faults > > after the page is mlock()d, then we need the ->page_mkwrite() call > > during the mlock() call. > > OK, so I'm not an mm hacker, so maybe I'm missing something. Could > part of this be fixed by simply sending the write faults for > mlock()'ed pages, so page_mkwrite() gets called when the page is > dirtied. Seems like a real waste to have the file system pre-allocate > all of the blocks for a mlock()'ed region. Why does mlock() have to > result in the write faults getting suppressed when the page is > actually dirtied? Yup, I don't think it would be too bad to take a minor fault each time an mlocked page transitions from clean->dirty. In fact we should already be doing that, after the mlocked page gets written back by kupdate? Hope so! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org