From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f177.google.com (mail-ig0-f177.google.com [209.85.213.177]) by kanga.kvack.org (Postfix) with ESMTP id 567266B0070 for ; Thu, 19 Mar 2015 14:09:16 -0400 (EDT) Received: by igcau2 with SMTP id au2so15564809igc.1 for ; Thu, 19 Mar 2015 11:09:16 -0700 (PDT) Received: from mail-ig0-x234.google.com (mail-ig0-x234.google.com. [2607:f8b0:4001:c05::234]) by mx.google.com with ESMTPS id 82si2075960ioz.62.2015.03.19.11.09.15 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 19 Mar 2015 11:09:15 -0700 (PDT) Received: by ignm3 with SMTP id m3so15633818ign.0 for ; Thu, 19 Mar 2015 11:09:15 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20150319141022.GD3087@suse.de> References: <20150312131045.GE3406@suse.de> <20150312184925.GH3406@suse.de> <20150317070655.GB10105@dastard> <20150317205104.GA28621@dastard> <20150317220840.GC28621@dastard> <20150319141022.GD3087@suse.de> Date: Thu, 19 Mar 2015 11:09:15 -0700 Message-ID: Subject: Re: [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur From: Linus Torvalds Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Dave Chinner , Ingo Molnar , Andrew Morton , Aneesh Kumar , Linux Kernel Mailing List , Linux-MM , xfs@oss.sgi.com, ppc-dev On Thu, Mar 19, 2015 at 7:10 AM, Mel Gorman wrote: > - if (!pmd_dirty(pmd)) > + /* See similar comment in do_numa_page for explanation */ > + if (!(vma->vm_flags & VM_WRITE)) Yeah, that would certainly be a whole lot more obvious than all the "if this particular pte/pmd looks like X" tests. So that, together with scanning rate improvements (this *does* seem to be somewhat chaotic, so it's quite possible that the current scanning rate thing is just fairly unstable) is likely the right thing. I'd just like to _understand_ why that write/dirty bit makes such a difference. I thought I understood what was going on, and was happy, and then Dave come with his crazy numbers. Damn you Dave, and damn your numbers and "facts" and stuff. Sometimes I much prefer ignorant bliss. Linus -- 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