From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f47.google.com (mail-ee0-f47.google.com [74.125.83.47]) by kanga.kvack.org (Postfix) with ESMTP id 62A166B0036 for ; Tue, 8 Apr 2014 10:46:33 -0400 (EDT) Received: by mail-ee0-f47.google.com with SMTP id b15so772915eek.6 for ; Tue, 08 Apr 2014 07:46:31 -0700 (PDT) Received: from mail.zytor.com (terminus.zytor.com. [2001:1868:205::10]) by mx.google.com with ESMTPS id w48si3039892eel.356.2014.04.08.07.46.29 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 08 Apr 2014 07:46:30 -0700 (PDT) Message-ID: <53440A5D.6050301@zytor.com> Date: Tue, 08 Apr 2014 07:40:29 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [RFC PATCH 0/5] Use an alternative to _PAGE_PROTNONE for _PAGE_NUMA v2 References: <1396962570-18762-1-git-send-email-mgorman@suse.de> In-Reply-To: <1396962570-18762-1-git-send-email-mgorman@suse.de> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman , Linux-X86 Cc: Linus Torvalds , Cyrill Gorcunov , Ingo Molnar , Steven Noonan , Rik van Riel , David Vrabel , Andrew Morton , Peter Zijlstra , Andrea Arcangeli , Dave Hansen , Srikar Dronamraju , Linux-MM , LKML David Vrabel On 04/08/2014 06:09 AM, Mel Gorman wrote: > Using unused physical bits is something that will break eventually. > > Changelog since V1 > o Reuse software-bits > o Use paravirt ops when modifying PTEs in the NUMA helpers > > Aliasing _PAGE_NUMA and _PAGE_PROTNONE had some convenient properties but > it ultimately gave Xen a headache and pisses almost everybody off that > looks closely at it. Two discussions on "why this makes sense" is one > discussion too many so rather than having a third so here is this series. > This series reuses the PTE bits that are available to the programmer. > This adds some contraints on how and when automatic NUMA balancing can be > enabled but it should go away again when Xen stops using _PAGE_IOMAP. > > The series also converts the NUMA helpers to use paravirt-friendly operations > but it needs a Tested-by from the Xen and powerpc people. > It is proably simpler to just base this patchset on top of David Vrabel's which actually *does* remove _PAGE_IOMAP. David, is your patchset going to be pushed in this merge window as expected? That being said, these bits are precious, and if this ends up being a case where "only Xen needs another bit" once again then Xen should expect to get kicked to the curb at a moment's notice. -hpa -- 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