Messages in this thread | | | Date | Fri, 06 Jun 2008 08:09:55 +0200 | From | <> | Subject | [RFC -mm 0/6] sysv ipc: scale msgmnb with the number of cpus |
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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
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
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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(-)
-- Solofo Ramangalahy Bull SA.
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