From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by rv-out-0708.google.com with SMTP id f25so2257767rvb.26 for ; Tue, 20 May 2008 07:56:48 -0700 (PDT) Message-ID: Date: Tue, 20 May 2008 16:56:48 +0200 From: "Michael Kerrisk" Subject: Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem 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: owner-linux-mm@kvack.org Return-Path: To: Nadia Derbey Cc: Linux Kernel Mailing List , linux-mm@kvack.org List-ID: [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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org