From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f45.google.com (mail-ee0-f45.google.com [74.125.83.45]) by kanga.kvack.org (Postfix) with ESMTP id 1FB5B6B0031 for ; Wed, 9 Apr 2014 02:21:11 -0400 (EDT) Received: by mail-ee0-f45.google.com with SMTP id d17so1439415eek.4 for ; Tue, 08 Apr 2014 23:21:10 -0700 (PDT) Received: from mail-ee0-x22f.google.com (mail-ee0-x22f.google.com [2a00:1450:4013:c00::22f]) by mx.google.com with ESMTPS id l41si5661eef.158.2014.04.08.23.21.08 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 08 Apr 2014 23:21:09 -0700 (PDT) Received: by mail-ee0-f47.google.com with SMTP id b15so1426901eek.34 for ; Tue, 08 Apr 2014 23:21:07 -0700 (PDT) Date: Wed, 9 Apr 2014 08:21:03 +0200 From: Ingo Molnar Subject: Re: [RFC PATCH 0/5] Use an alternative to _PAGE_PROTNONE for _PAGE_NUMA v2 Message-ID: <20140409062103.GA7294@gmail.com> References: <1396962570-18762-1-git-send-email-mgorman@suse.de> <53440A5D.6050301@zytor.com> <20140408164652.GL7292@suse.de> <20140408173031.GS10526@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140408173031.GS10526@twins.programming.kicks-ass.net> Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: Mel Gorman , Linus Torvalds , "H. Peter Anvin" , Linux-X86 , Cyrill Gorcunov , Steven Noonan , Rik van Riel , David Vrabel , Andrew Morton , Andrea Arcangeli , Dave Hansen , Srikar Dronamraju , Linux-MM , LKML * Peter Zijlstra wrote: > On Tue, Apr 08, 2014 at 05:46:52PM +0100, Mel Gorman wrote: > > Someone will ask why automatic NUMA balancing hints do not use "real" > > PROT_NONE but as it would need VMA information to do that on all > > architectures it would mean that VMA-fixups would be required when marking > > PTEs for NUMA hinting faults so would be expensive. > > Like this: > > https://lkml.org/lkml/2012/11/13/431 > > That used the generic PROT_NONE infrastructure and compared, on fault, > the page protection bits against the vma->vm_page_prot bits? > > So the objection to that approach was the vma-> dereference in > pte_numa() ? I think the real underlying objection was that PTE_NUMA was the last leftover from AutoNUMA, and removing it would have made it not a 'compromise' patch set between 'AutoNUMA' and 'sched/numa', but would have made the sched/numa approach 'win' by and large. The whole 'losing face' annoyance that plagues all of us (me included). I didn't feel it was important to the general logic of adding access pattern aware NUMA placement logic to the scheduler, and I obviously could not ignore the NAKs from various mm folks insisting on PTE_NUMA, so I conceded that point and Mel built on that approach as well. Nice it's being cleaned up, and I'm pretty happy about how NUMA balancing ended up looking like. Thanks, Ingo -- 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