From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx143.postini.com [74.125.245.143]) by kanga.kvack.org (Postfix) with SMTP id BA3AF6B0072 for ; Tue, 4 Dec 2012 19:39:01 -0500 (EST) Message-ID: <1354667937.6733.233.camel@calx> Subject: Re: [RFC PATCH 0/2] mm: Add ability to monitor task's memory changes From: Matt Mackall Date: Tue, 04 Dec 2012 18:38:57 -0600 In-Reply-To: <20121204162411.700d4954.akpm@linux-foundation.org> References: <50B8F2F4.6000508@parallels.com> <20121203144310.7ccdbeb4.akpm@linux-foundation.org> <50BD86DE.6050700@parallels.com> <20121204152121.e5c33938.akpm@linux-foundation.org> <1354666628.6733.227.camel@calx> <20121204162411.700d4954.akpm@linux-foundation.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Pavel Emelyanov , Hugh Dickins , KAMEZAWA Hiroyuki , Michal Hocko , Mel Gorman , Johannes Weiner , Linux MM , Rik van Riel , Wu Fengguang On Tue, 2012-12-04 at 16:24 -0800, Andrew Morton wrote: > On Tue, 04 Dec 2012 18:17:08 -0600 > Matt Mackall wrote: > > > On Tue, 2012-12-04 at 15:21 -0800, Andrew Morton wrote: > > > On Tue, 04 Dec 2012 09:15:10 +0400 > > > Pavel Emelyanov wrote: > > > > > > > > > > > > Two alternatives come to mind: > > > > > > > > > > 1) Use /proc/pid/pagemap (Documentation/vm/pagemap.txt) in some > > > > > fashion to determine which pages have been touched. > > > > [momentarily coming out of kernel retirement for old man rant] > > > > This is a popular interface anti-pattern. > > > > You shouldn't use an interface that gives you huge amount of STATE to > > detect small amounts of CHANGE via manual differentiation. > > I'm not sure that's what checkpoint-restart will be doing. If we want > to determine "which pages have been touched since the last checkpoint > ten minutes ago" then that set of touched pages *is* state. And it's > not "small"! Yeah, there is definitely a middle-ground here between "I want high-frequency updates" and "I want to see the whole picture". The filesystem analogy is backups: we don't have any good way to say "find me all files changed since yesterday" short of "find all files". The closest thing is explicit snapshotting. -- Mathematics is the supreme nostalgia of our time. -- 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