Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764463AbYFFGTg (ORCPT ); Fri, 6 Jun 2008 02:19:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1764535AbYFFGRr (ORCPT ); Fri, 6 Jun 2008 02:17:47 -0400 Received: from ecfrec.frec.bull.fr ([129.183.4.8]:59299 "EHLO ecfrec.frec.bull.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753425AbYFFGRq (ORCPT ); Fri, 6 Jun 2008 02:17:46 -0400 Message-Id: <20080606060958.873465466@bull.net> References: <20080606060955.317871352@bull.net> User-Agent: quilt/0.46-1 Date: Fri, 06 Jun 2008 08:10:01 +0200 From: To: Cc: Solofo Ramangalahy Subject: [RFC -mm 6/6] sysv ipc: documentation for msgmnb scaling wrt. cpus Content-Disposition: inline; filename=ipc-documentation-scale-msgmnb-with-the-number-of-cpus.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1837 Lines: 59 From: Solofo Ramangalahy Add documentation to explain how to disable and reenable the computation mechanism. Signed-off-by: Solofo Ramangalahy --- Documentation/sysctl/kernel.txt | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) Index: b/Documentation/sysctl/kernel.txt =================================================================== --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -179,6 +179,33 @@ kernel stack. ============================================================== +msgmnb + +Maximum size in bytes, not in message count, of a single SystemV IPC +message queue (b stands for bytes). + +This value is dynamic and depends on the online cpu count of the +machine (taking cpu hotplug into account). + +Computed values are between MSGMNB and MSGMNB*MSG_CPU_SCALE #define +constants (currently [16384,65536]). + +The exact value is automatically (re)computed, but: +. If the value is positioned from user space (via procfs or sysctl()), + to a positive value then the automatic recomputation is + disabled. This leaves control to user space. E.g. + + # echo 16384 > /proc/sys/kernel/msgmnb + +. If the value is positioned from user space to a negative value, then + the computation is reenabled. E.g. + + # echo -1 > /proc/sys/kernel/msgmnb + +See recompute_msgmnb() function in ipc/ directory for details. + +============================================================== + osrelease, ostype & version: # cat osrelease -- Solofo Ramangalahy Bull SA. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/