From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx189.postini.com [74.125.245.189]) by kanga.kvack.org (Postfix) with SMTP id 17B466B004D for ; Mon, 19 Mar 2012 09:26:59 -0400 (EDT) Message-ID: <1332163594.18960.335.camel@twins> Subject: Re: [RFC][PATCH 00/26] sched/numa From: Peter Zijlstra Date: Mon, 19 Mar 2012 14:26:34 +0100 In-Reply-To: <20120319130401.GI24602@redhat.com> References: <20120316144028.036474157@chello.nl> <4F670325.7080700@redhat.com> <1332155527.18960.292.camel@twins> <20120319130401.GI24602@redhat.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Avi Kivity , Linus Torvalds , Andrew Morton , Thomas Gleixner , Ingo Molnar , Paul Turner , Suresh Siddha , Mike Galbraith , "Paul E. McKenney" , Lai Jiangshan , Dan Smith , Bharata B Rao , Lee Schermerhorn , Rik van Riel , Johannes Weiner , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Mon, 2012-03-19 at 14:04 +0100, Andrea Arcangeli wrote: > About the cost of the actual pagetable scanner, you're not being > rational about it. You should measure it for once, take khugepaged > make it scan 1G of memory per millisecond and measure the cost. Death by a thousand cuts..=20 > You keep complaining about the unaccountability of the pagetable > scanners in terms of process load, and that's a red herring as far as > I can tell. The irqs and ksoftirqd load in a busy server, is likely > much higher than whatever happens at the pagetable scanner level (sure > thing for khugepaged and by an huge order of magnitude so).=20 Who says I agree with ksoftirqd? I would love to get rid of all things softirq. And I also think workqueues are over-/ab-used. > I don't > think this is a relevant concern anyway because the pagetable scanners > go over all memory in a equal amount so the cost would be evenly > distributed for all processes over time (the same cannot be said about > the irqs and ksoftrqid that will benefit only a few processes doing > I/O).=20 So what about the case where all I do is compile kernels and we already have near perfect locality because everything is short running? You're still scanning that memory, and I get no benefit. -- 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 internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org