From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932637AbYETO2h (ORCPT ); Tue, 20 May 2008 10:28:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755559AbYETO23 (ORCPT ); Tue, 20 May 2008 10:28:29 -0400 Received: from rv-out-0506.google.com ([209.85.198.224]:47818 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755084AbYETO22 (ORCPT ); Tue, 20 May 2008 10:28:28 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=message-id:date:from:to:subject:cc:mime-version:content-type:content-transfer-encoding:content-disposition; b=e3qhkuR1rb9QpObUDuTyUyl3wHLJ3kBERjanMZ2W01m+mQBU5Kidc6VPF3RGhqu5GYqJXROvgzcj2++5nZ6NtFCzWZIVSgBt0QGSk3CWHNynPUduXXykr1y0hJMxDxyZ8g5zmqYbLe7E8hbu2lQFQv4G/QB5IkEfbbZpJqdISQw= Message-ID: Date: Tue, 20 May 2008 16:28:27 +0200 From: "Michael Kerrisk" To: Nadia.Derbey@bull.net Subject: Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem Cc: "Linux Kernel Mailing List" , linux-mm@vger.kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Nadia, Regarding your: [PATCH 1/8] Scaling msgmni to the amount of lowmem http://article.gmane.org/gmane.linux.kernel/637849/ which I see has made its way in 2.6.26-rc Your patch has the following change: -#define MSGPOOL (MSGMNI*MSGMNB/1024) /* size in kilobytes of message pool */ +#define MSGPOOL (MSGMNI * MSGMNB) /* size in bytes of message pool */ Since this constitutes a kernel-userland interface change, so please do CC me, so that I can change the man pages if needed. The man page (http://www.kernel.org/doc/man-pages/online/pages/man2/msgctl.2.html) does indeed say that msgpool is "unused". But that meant "unused by the kernel" (sorry -- I probably should have worded that text better). And, as you spotted, the page also wrongly said the value is in bytes. However, making this change affects the ABI. A userspace application that was previously using msgctl(IPC_INFO) to retrieve the msgpool field will be affected by the factor-of-1024 change. I strongly suspect that there no such applications, or certainly none that care (since this value is unused by the kernel). But was there a reason for making this change, aside from the fact that the code and the man page didn't agree? Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html