From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756595AbYH1Acr (ORCPT ); Wed, 27 Aug 2008 20:32:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754418AbYH1Acj (ORCPT ); Wed, 27 Aug 2008 20:32:39 -0400 Received: from smtp101.mail.mud.yahoo.com ([209.191.85.211]:26760 "HELO smtp101.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754049AbYH1Aci (ORCPT ); Wed, 27 Aug 2008 20:32:38 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:X-Yahoo-Newman-Property:From:To:Subject:Date:User-Agent:Cc:References:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Content-Disposition:Message-Id; b=4XhaZ8GnmUGj5dZ82+XF1IliMo16he4JbCvnY51W8jzNVgJWkvWC7rI8Yq6iYUd7/p10IITC+VPjiQ65rW+W7wHxVuJOsUKNqTsn34JpR/Ga5q9cy9aXgTkjTc2OBwYDRHXsKboo90Br9hD0DiTW/ykzXhXS2Pco7gHtO26bki8= ; X-YMail-OSG: 7FqErjUVM1nbAKLgXfFEfD.SnsJnvRw4lNvP5E0nqsIelzQ.rwOtFVhJxtF9tSsQO5HXf2mZEIVnWdr13wJwMKhlx3lmwPjF4MAydnyr53sSMWbZ6pgiu2nbENc1GBq5UkE- X-Yahoo-Newman-Property: ymail-3 From: Nick Piggin To: Jeremy Fitzhardinge Subject: Re: Definition of x86 _PAGE_SPECIAL and sharing _PAGE_UNUSED1 Date: Thu, 28 Aug 2008 10:32:30 +1000 User-Agent: KMail/1.9.5 Cc: Ingo Molnar , Hugh Dickens , Linux Kernel Mailing List , Andrew Morton , Linux Memory Management List References: <48B5A4B0.9050308@goop.org> In-Reply-To: <48B5A4B0.9050308@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200808281032.30594.nickpiggin@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 28 August 2008 05:02, Jeremy Fitzhardinge wrote: > _PAGE_SPECIAL is overloading _PAGE_UNUSED1. Does it really leave > _PAGE_UNUSED1 available for other uses, or does it become an exclusive > user of that flag. Under what circumstances can they be shared? > > arch/x86/mm/pageattr-test.c is now using _PAGE_UNUSED1 as the flag used > to make sure that huge pages are shattered properly (previously it used > _PAGE_GLOBAL). Is that going to clash with _PAGE_SPECIAL? Ah... pity it was hidden away there and not put into the include file. > In other words, should we drop _PAGE_UNUSED1 altogether, or at least > define how the its different users can coexist? I don't feel strongly about it. But you should put your definition in pgtable.h (and possibly explain how it coexists with _SPECIAL). > Am I right in supposing that _PAGE_SPECIAL can only be set on user pages? Yes. > (Also, "SPECIAL" is awfully generic. Was there really no more > descriptive name for this?) I thought it was about on par with its counterpart, which is "normal". Either way, I don't think a casual reader would get an adequate idea of how it works in one word. normal ~= refcounted, special ~= !refcounted I guess, but it is slightly more than that and besides, normal was there first, and I think Linus coined it... if you can convince him to change it then you have my blessing to change special into whatever you want.