From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757499AbYH1Arp (ORCPT ); Wed, 27 Aug 2008 20:47:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755027AbYH1Arg (ORCPT ); Wed, 27 Aug 2008 20:47:36 -0400 Received: from gw.goop.org ([64.81.55.164]:50877 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754880AbYH1Arg (ORCPT ); Wed, 27 Aug 2008 20:47:36 -0400 Message-ID: <48B5F5A6.4060309@goop.org> Date: Wed, 27 Aug 2008 17:47:34 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.16 (X11/20080723) MIME-Version: 1.0 To: Nick Piggin CC: Ingo Molnar , Hugh Dickens , Linux Kernel Mailing List , Andrew Morton , Linux Memory Management List Subject: Re: Definition of x86 _PAGE_SPECIAL and sharing _PAGE_UNUSED1 References: <48B5A4B0.9050308@goop.org> <200808281032.30594.nickpiggin@yahoo.com.au> In-Reply-To: <200808281032.30594.nickpiggin@yahoo.com.au> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Nick Piggin wrote: > Ah... pity it was hidden away there and not put into the include file. > Yes. I just prepped a patch to bring it out into the light. > I don't feel strongly about it. But you should put your definition in > pgtable.h (and possibly explain how it coexists with _SPECIAL). > Yes, that was my plan, but without knowing how _SPECIAL is used, it's a bit tricky. Is there a comment somewhere which describes who sets it and when? From a quick look, it seems it's set on newly added user pages which aren't COWed. Can they be shared file-backed pages? Anonymous pages? Device pages? >> Am I right in supposing that _PAGE_SPECIAL can only be set on user pages? >> > > Yes. > OK, that won't clash with CPA tests at all, since they're kernel only. >> (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. > It's only used in a couple of places, so giving it a longer name wouldn't cost much. _PAGE_USER_UNCOUNTED? But ugh, a lot of cross-arch churnpatch to do it. J