From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: When should ralloc.c be used? Date: Fri, 28 Oct 2016 15:25:27 +0300 Message-ID: <83a8dosls8.fsf@gnu.org> References: <838ttfnmev.fsf@gnu.org> <837f8znk8f.fsf@gnu.org> <83zilvm2ud.fsf@gnu.org> <83r377m0i8.fsf@gnu.org> <83eg36n6v5.fsf@gnu.org> <83shrl523p.fsf@gnu.org> <83eg354ux3.fsf@gnu.org> <4f0c2868-d408-a5c4-d5a8-90dae750eb33@dancol.org> <878tt9ggdk.fsf@ritchie.wxcvbn.org> <83k2cssypt.fsf@gnu.org> <6350b2df-fde9-e716-d279-9f29438f8ee5@dancol.org> <83d1ikswsf.fsf@gnu.org> <7ab47b94-c662-1351-0dd3-ed5269842438@dancol.org> <83bmy4stax.fsf@gnu.org> Reply-To: Eli Zaretskii NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1477657555 31090 195.159.176.226 (28 Oct 2016 12:25:55 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 28 Oct 2016 12:25:55 +0000 (UTC) Cc: eggert@cs.ucla.edu, monnier@iro.umontreal.ca, emacs-devel@gnu.org To: Daniel Colascione Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Fri Oct 28 14:25:51 2016 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1c06E2-0005lB-9s for ged-emacs-devel@m.gmane.org; Fri, 28 Oct 2016 14:25:34 +0200 Original-Received: from localhost ([::1]:48867 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c06E4-000538-R8 for ged-emacs-devel@m.gmane.org; Fri, 28 Oct 2016 08:25:36 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:34767) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c06Dw-00050a-Bd for emacs-devel@gnu.org; Fri, 28 Oct 2016 08:25:29 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c06Ds-0002ZU-C4 for emacs-devel@gnu.org; Fri, 28 Oct 2016 08:25:28 -0400 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:58729) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c06Ds-0002ZQ-8e; Fri, 28 Oct 2016 08:25:24 -0400 Original-Received: from 84.94.185.246.cable.012.net.il ([84.94.185.246]:3939 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_128_CBC_SHA1:128) (Exim 4.82) (envelope-from ) id 1c06Dr-0000SU-2P; Fri, 28 Oct 2016 08:25:23 -0400 In-reply-to: (message from Daniel Colascione on Fri, 28 Oct 2016 02:52:19 -0700) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2001:4830:134:3::e X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:208937 Archived-At: > Cc: monnier@iro.umontreal.ca, eggert@cs.ucla.edu, emacs-devel@gnu.org > From: Daniel Colascione > Date: Fri, 28 Oct 2016 02:52:19 -0700 > > > If reserving a range of addresses doesn't necessarily mean they will > > be later available for committing, then what is the purpose of > > reserving them in the first place? What good does it do? > > Reserving address space is useful for making sure you have a contiguous > range of virtual addresses that you can use later. But if committing more pages from the reserved range is not guaranteed to succeed, I cannot rely on getting that contiguous range of addresses, can I? > > We have in w32heap.c:mmap_realloc code that attempts to commit pages > > that were previously reserved. That code does recover from a failure > > to commit, but such a failure is deemed unusual and causes special > > warnings under debugger. I never saw these warnings happen, except > > when we had bugs in that code. You seem to say that this is based on > > false premises, and there's nothing unusual about MEM_COMMIT to fail > > for the range of pages previously reserved with MEM_RESERVE. > > The MEM_COMMIT failure might be rare in practice --- systems have a lot > of memory these days --- but MEM_COMMIT failing for a memory region > previously reserved with MEM_RESERVE is perfectly legal. I can only say that I never saw that happening. Thanks.