From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 14 Apr 2006 09:01:18 -0700 (PDT) From: Christoph Lameter Subject: Re: [PATCH 2/5] Swapless V2: Add migration swap entries In-Reply-To: <20060413222516.4cb5885c.akpm@osdl.org> Message-ID: References: <20060413235406.15398.42233.sendpatchset@schroedinger.engr.sgi.com> <20060413235416.15398.49978.sendpatchset@schroedinger.engr.sgi.com> <20060413171331.1752e21f.akpm@osdl.org> <20060413174232.57d02343.akpm@osdl.org> <20060413180159.0c01beb7.akpm@osdl.org> <20060413181716.152493b8.akpm@osdl.org> <20060413222516.4cb5885c.akpm@osdl.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: hugh@veritas.com, linux-kernel@vger.kernel.org, lee.schermerhorn@hp.com, linux-mm@kvack.org, taka@valinux.co.jp, marcelo.tosatti@cyclades.com, kamezawa.hiroyu@jp.fujitsu.com List-ID: On Thu, 13 Apr 2006, Andrew Morton wrote: > > We would have to take that for each task mapping the page. Very expensive > > operation. > > So... why does do_migrate_pages() take mmap_sem at all? In order to scan for migratable pages through the page table and in order to guarantee the existence of the anon vma. > And the code we're talking about here deals with anonymous pages, which are > not shared betweem mm's. COW f.e. results in sharing. Hmmm.. But I see the point the "optimization" causes an inconsistency between anon and file backed pages. For anon pages we need to do this polling. I had prior unoptimized version that modified lookup_swap_cache to handle migration entries. Maybe we better undo the optimization. -- 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/ . Don't email: email@kvack.org