Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761883AbYFXPPu (ORCPT ); Tue, 24 Jun 2008 11:15:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760575AbYFXPPl (ORCPT ); Tue, 24 Jun 2008 11:15:41 -0400 Received: from ecfrec.frec.bull.fr ([129.183.4.8]:47652 "EHLO ecfrec.frec.bull.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755469AbYFXPPj (ORCPT ); Tue, 24 Jun 2008 11:15:39 -0400 Message-Id: <20080624093452.946878437@bull.net> User-Agent: quilt/0.46-1 Date: Tue, 24 Jun 2008 11:34:52 +0200 From: To: Andrew Morton Cc: , Matt Helsley , Mingming Cao , Nadia Derbey , Manfred Spraul , Nick Piggin Subject: [PATCH -mm 0/3] sysv ipc: increase msgmnb with the number of cpus Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4192 Lines: 100 The size in bytes of a SysV IPC message queue, msgmnb, is too small for large machines, but we don't want to bloat small machines. This series change ("scale") the default value of /proc/sys/kernel/msgmnb. Several methods are used already to modify (mainly increase) msgmnb: . distribution specific patch (e.g. openSUSE) . system wide sysctl.conf . application specific tuning via /proc/sys/kernel/msgmnb Integrating this series would: . reflect hardware and software evolutions and diversity, . reduce configuration/tuning for the applications. Here is the timeline of the evolution of MSG* #defines: Year 1994 1999 1999 2008 Version 1.0 2.3.27 2.3.30 2.6.24 #define MSGMNI 128 128 16 16 #define MSGMAX 4056 8192 8192 8192 #define MSGMNB 16384 16384 16384 16384 This patch series increases msgmnb with respect to the number of cpus/cores for larger machines. For uniprocessor machines the value does not increase. This series is similar to (and depends on) the series which scales msgmni, the number of IPC message queue identifiers, to the amount of low memory. While Nadia's previous series scaled msgmni along the memory axis, hence the message pool (msgmni x msgmnb), this series uses a second axis: the number of online CPUs. As well as covering the (cpu,memory) space of machines size, this reflects the parallelism allowed by lockless send/receive for in-flight messages in queues (msgmnb / msgmax messages). The initial scaling is done at initialization of the ipc namespace. Furthermore, the value becomes dynamic with respect to cpu hotplug, decreasing/increasing when a cpu is taken offline/online. The msgmni and msgmnb values become dependent, as the value of msgmni is computed with respect to the value of msgmnb. Other solutions could be possible, like using a dbus/hal daemon. This patches seems light enough not to go to user space. In particular, the computation formula is simple. The series is as follows: . patch 1 introduces the scaling function . patch 2 deals with cpu hotplug . patch 3 finer grain disabling/reenabling scaling mechanism (disconnect msgmnb and msgmni) --- The series applies to 2.6.26-rc5-mm3 Compared to the RFC, the following changes have been made: . reduce use of "scale" word which leads to confusion about the fact that this is not directly a performance patch [Nick] . mention that the formula is simple, not needing logarithm (or user space) [Nick] . example of distribution using patch [Manfred] . mention hal/dbus daemon [Manfred] . do not reenable msgmni recomputation when reenabling msgmnb. It suffices to do a one shot recomputation [Nadia] . patch 3 and 4 have been merged with patch 1 [Nadia] . Integrated documentation with patch [Matt] Thanks for the help! . corrected a bug in the last patch (forgot to add braces when adding statement in if) The last remark of Nadia about the third patch has not been addressed (other than keeping it like that): "Doing this, we are completly loosing the benefits of the notification chains: since the the notifier blocks remain registered + we are unconditionally adding a test at the top of each recompute routine. But the other choice would have been to define another notifier chain dedicated to msgmnb. I'm not convinced about what is the best solution?" Documentation/sysctl/kernel.txt | 27 +++++++++++++++++++ include/linux/ipc_namespace.h | 4 ++ include/linux/msg.h | 5 +++ ipc/ipc_sysctl.c | 56 ++++++++++++++++++++++++++++++---------- ipc/ipcns_notifier.c | 23 ++++++---------- ipc/msg.c | 23 +++++++++++++--- ipc/util.c | 28 ++++++++++++++++++++ ipc/util.h | 1 8 files changed, 135 insertions(+), 32 deletions(-) -- -- 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/