From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id 93B916B00AA for ; Wed, 17 Nov 2010 07:58:25 -0500 (EST) Date: Wed, 17 Nov 2010 23:57:56 +1100 From: Nick Piggin Subject: Re: [PATCH 3/3] mlock: avoid dirtying pages and triggering writeback Message-ID: <20101117125756.GA5576@amd> References: <1289996638-21439-1-git-send-email-walken@google.com> <1289996638-21439-4-git-send-email-walken@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1289996638-21439-4-git-send-email-walken@google.com> Sender: owner-linux-mm@kvack.org To: Michel Lespinasse Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Hugh Dickins , Rik van Riel , Kosaki Motohiro , Peter Zijlstra , Nick Piggin , Theodore Tso , Michael Rubin , Suleiman Souhlal List-ID: On Wed, Nov 17, 2010 at 04:23:58AM -0800, Michel Lespinasse wrote: > When faulting in pages for mlock(), we want to break COW for anonymous > or file pages within VM_WRITABLE, non-VM_SHARED vmas. However, there is > no need to write-fault into VM_SHARED vmas since shared file pages can > be mlocked first and dirtied later, when/if they actually get written to. > Skipping the write fault is desirable, as we don't want to unnecessarily > cause these pages to be dirtied and queued for writeback. It's not just to break COW, but to do block allocation and such (filesystem's page_mkwrite op). That needs to at least be explained in the changelog. Filesystem doesn't have a good way to fully pin required things according to mlock, but page_mkwrite provides some reasonable things (like block allocation / reservation). -- 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