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Date: Fri, 6 Jun 2008 18:23:22 +1000 From: Nick Piggin <nickpiggin@...oo.com.au> To: Solofo.Ramangalahy@...l.net Cc: linux-kernel@...r.kernel.org Subject: Re: [RFC -mm 0/6] sysv ipc: scale msgmnb with the number of cpus On Friday 06 June 2008 16:09, Solofo.Ramangalahy@...l.net wrote: > 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 What's your evidence for this? Can you provide before / after performance numbers? Also, when scaling things like this, it is probably more usual to use a log scale rather than linear, so that's a thought. > > Several methods are used already to modify (mainly increase) msgmnb: > . distribution specific patch > . 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 scales 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. > > The msgmni and msgmnb values become dependent, as the value of msgmni > is computed with respect to the value of msgmnb. > > The series is as follows: > . patch 1 introduces the scaling function > . patch 2 deals with cpu hotplug > . patch 3 allows user space to disable the scaling mechanism > . patch 4 allows user space to reenable the scaling mechanism > . patch 5 finer grain disabling/reenabling scaling mechanism > (disconnect msgmnb and msgmni) > . patch 6 adds documentation > > --- > > The series applies to 2.6.26-rc2-mm1 + patch suppressing KERN_INFO > messages as discussed at: > http://article.gmane.org/gmane.linux.kernel/686229 > "[PATCH 1/1] Only output msgmni value at boot time" > (in mmotm: ipc-only-output-msgmni-value-at-boot-time.patch) > > The plan would be to have this ready for the 2.6.27 merge window if > there are no objections. > > Documentation/sysctl/kernel.txt | 27 ++++++++++++++++++++++ > include/linux/ipc_namespace.h | 4 ++- > include/linux/msg.h | 5 ++++ > ipc/ipc_sysctl.c | 48 > ++++++++++++++++++++++++++++++---------- ipc/ipcns_notifier.c | > 23 +++++++------------ > ipc/msg.c | 25 +++++++++++++++++--- > ipc/util.c | 28 +++++++++++++++++++++++ > ipc/util.h | 1 > 8 files changed, 131 insertions(+), 30 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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