From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756290AbbCRRbc (ORCPT ); Wed, 18 Mar 2015 13:31:32 -0400 Received: from mail-ig0-f180.google.com ([209.85.213.180]:33071 "EHLO mail-ig0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753576AbbCRRb3 (ORCPT ); Wed, 18 Mar 2015 13:31:29 -0400 MIME-Version: 1.0 In-Reply-To: References: <20150309191943.GF26657@destitution> <20150312131045.GE3406@suse.de> <20150312184925.GH3406@suse.de> <20150317070655.GB10105@dastard> <20150317205104.GA28621@dastard> <20150317220840.GC28621@dastard> Date: Wed, 18 Mar 2015 10:31:28 -0700 X-Google-Sender-Auth: dBRMYon28mut5KbMLpLajG773yM Message-ID: Subject: Re: [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur From: Linus Torvalds To: Dave Chinner Cc: Mel Gorman , Ingo Molnar , Andrew Morton , Aneesh Kumar , Linux Kernel Mailing List , Linux-MM , xfs@oss.sgi.com, ppc-dev Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 18, 2015 at 9:08 AM, Linus Torvalds wrote: > > So why am I wrong? Why is testing for dirty not the same as testing > for writable? > > I can see a few cases: > > - your load has lots of writable (but not written-to) shared memory Hmm. I tried to look at the xfsprog sources, and I don't see any MAP_SHARED activity. It looks like it's just using pread64/pwrite64, and the only MAP_SHARED is for the xfsio mmap test thing, not for xfsrepair. So I don't see any shared mappings, but I don't know the code-base. > - something completely different that I am entirely missing So I think there's something I'm missing. For non-shared mappings, I still have the idea that pte_dirty should be the same as pte_write. And yet, your testing of 3.19 shows that it's a big difference. There's clearly something I'm completely missing. Linus