From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933426AbYETO5L (ORCPT ); Tue, 20 May 2008 10:57:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933342AbYETO4u (ORCPT ); Tue, 20 May 2008 10:56:50 -0400 Received: from rv-out-0506.google.com ([209.85.198.230]:4525 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933337AbYETO4t (ORCPT ); Tue, 20 May 2008 10:56:49 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=ISIgdmEvvd3HUzUuK3dhg0Fqkp/38CyakD3T5FM7NXkEzsm4wZbCK3CR7jsaDhfMH9j+FaIUtPpTbHF0yiW2jgBfnILHIu376asZz1spnsMLv/wZsvagua0EQxu2qi5Apjnr4aSPT1PPyJtqXoHj+vqC/DNG92DUaIfuxQ7aHnA= Message-ID: Date: Tue, 20 May 2008 16:56:48 +0200 From: "Michael Kerrisk" To: "Nadia Derbey" Subject: Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem Cc: "Linux Kernel Mailing List" , linux-mm@kvack.org In-Reply-To: <4832E423.5040708@bull.net> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <4832E423.5040708@bull.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Fixing the bad list address in my initial mail: CC += linux-mm@kvack.org] On Tue, May 20, 2008 at 4:45 PM, Nadia Derbey wrote: > Michael Kerrisk wrote: >> >> 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. > > Oops, sorry for not doing it: I misunderstood the "unused" > >> >> 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? >> > > No, that was the only reason. > Should I repost a patch to set it back as it used to be? On the one hand, I'd be inclined to leave things as they were pre 2.6.26. On the other hand, I believe that on other systems that have the limit, msgpool is a limit in bytes. (But documentation of these details on other systems is very thin on the ground.) I wonder if anyone else has some knowledge here? -- 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