From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752889AbbCHSqQ (ORCPT ); Sun, 8 Mar 2015 14:46:16 -0400 Received: from mail-ie0-f177.google.com ([209.85.223.177]:40016 "EHLO mail-ie0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751831AbbCHSqM (ORCPT ); Sun, 8 Mar 2015 14:46:12 -0400 MIME-Version: 1.0 In-Reply-To: References: <1425741651-29152-1-git-send-email-mgorman@suse.de> <1425741651-29152-5-git-send-email-mgorman@suse.de> <20150307163657.GA9702@gmail.com> <20150308100223.GC15487@gmail.com> Date: Sun, 8 Mar 2015 11:46:10 -0700 X-Google-Sender-Auth: 5N2_5hU8Z1ym6EG9a25JOnqkoEI Message-ID: Subject: Re: [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur From: Linus Torvalds To: Ingo Molnar Cc: Mel Gorman , Dave Chinner , 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 Sun, Mar 8, 2015 at 11:35 AM, Linus Torvalds wrote: >> As a second hack (not to be applied), could we change: >> >> #define _PAGE_BIT_PROTNONE _PAGE_BIT_GLOBAL >> >> to: >> >> #define _PAGE_BIT_PROTNONE (_PAGE_BIT_GLOBAL+1) >> >> to double check that the position of the bit does not matter? > > Agreed. We should definitely try that. There's a second reason to do that, actually: the __supported_pte_mask thing, _and_ the pageattr stuff in __split_large_page() etc play games with _PAGE_GLOBAL. As does drivers/lguest for some reason. So looking at this all, there's a lot of room for confusion with _PAGE_GLOBAL. That kind of confusion would certainly explain the whole "the changes _look_ like they do the same thing, but don't" - because of silly semantic conflicts with PROTNONE vs GLOBAL. Linus