From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755587AbZCOGDv (ORCPT ); Sun, 15 Mar 2009 02:03:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751458AbZCOGDm (ORCPT ); Sun, 15 Mar 2009 02:03:42 -0400 Received: from gw.goop.org ([64.81.55.164]:42340 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750807AbZCOGDm (ORCPT ); Sun, 15 Mar 2009 02:03:42 -0400 Message-ID: <49BC9A3B.1070908@goop.org> Date: Sat, 14 Mar 2009 23:03:39 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: "H. Peter Anvin" CC: Yinghai Lu , Linux Kernel Mailing List Subject: Re: Latest brk patchset References: <49BC413B.5020104@zytor.com> <49BC4CAC.202@goop.org> <49BC5BCF.1070602@zytor.com> In-Reply-To: <49BC5BCF.1070602@zytor.com> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org H. Peter Anvin wrote: > On this subject, what is the point of the 64 K "slop space", and if it > is necessary, why not just put it as a RESERVE_BRK() somewhere (*with* a > significant comment as to its necessity) instead of putting it as a > hack in the linker script? > Specifically, its to deal with space taken by alignment constraints. At least some of the extend_brk() calls are page aligned, so that uses up to another 4k. There are other ways to deal with it (pass an alignment to RESERVE_BRK and have it add it into the total, or just assume the user knows to include alignment overheads), but it seemed more straightforward to add some padding in the linker script. After all, anything unused will get freed. (But, yes, it could probably be documented as such, and 64k is a somewhat arbitrary number.) J