Messages in this thread | | | Subject | Re: [PATCH 1/1] IPC - Do not use a negative value to re-enable msgmni automatic recomputing | From | Nadia Derbey <> | Date | Thu, 21 Aug 2008 08:27:29 +0200 |
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On Tue, 2008-07-22 at 03:34 -0700, Andrew Morton wrote: > On Fri, 04 Jul 2008 08:37:16 +0200 Nadia.Derbey@bull.net wrote: > > > Resending after fixing the issues pointed out by Matt. > > Now applies to 2.6.26-rc8-mm1. > > > > [PATCH 01/01] > > > > This patch proposes an alternative to the "magical positive-versus-negative > > number trick" Andrew complained about last week in > > http://lkml.org/lkml/2008/6/24/418. > > > > This had been introduced with the patches that scale msgmni to the amount of > > lowmem. With these patches, msgmni has a registered notification routine > > that recomputes msgmni value upon memory add/remove or ipc namespace creation/ > > removal. > > > > When msgmni is changed from user space (i.e. value written to the proc file), > > that notification routine is unregistered, and the way to make it registered > > back is to write a negative value into the proc file. This is the "magical > > positive-versus-negative number trick". > > > > To fix this, a new proc file is introduced: /proc/sys/kernel/auto_msgmni. > > This file acts as ON/OFF for msgmni automatic recomputing. > > > > With this patch, the process is the following: > > 1) kernel boots in "automatic recomputing mode" > > /proc/sys/kernel/msgmni contains the value that has been computed (depends > > on lowmem) > > /proc/sys/kernel/automatic_msgmni contains "1" > > > > 2) echo <val> > /proc/sys/kernel/msgmni > > . sets msg_ctlmni to <val> > > . de-activates automatic recomputing (i.e. if, say, some memory is added > > msgmni won't be recomputed anymore) > > . /proc/sys/kernel/automatic_msgmni now contains "0" > > > > 3) echo "0" > /proc/sys/kernel/automatic_msgmni > > . de-activates msgmni automatic recomputing > > this has the same effect as 2) except that msg_ctlmni's value stays > > blocked at its current value) > > > > 3) echo "1" > /proc/sys/kernel/automatic_msgmni > > . recomputes msgmni's value based on the current available memory size > > and number of ipc namespaces > > . re-activates automatic recomputing for msgmni. > > > > Sigh. I suppose it's a bit better. > > > --- > > include/linux/ipc_namespace.h | 3 + > > ipc/ipc_sysctl.c | 72 ++++++++++++++++++++++++++++++++++-------- > > ipc/ipcns_notifier.c | 20 ++++++++--- > > Could we get this all documented for our poor users please? > > Documentation/filesystems/proc.txt is probably the most appropriate > place. > >
Sorry for answering so late, but I just came back from a looooong vacation. Actually, I first thought of documenting this new file in proc.txt, but didn't find anything related to the ipc tunables there, that's why I finally gave up with the idea. I'll send an update of the proc.txt as soon as possible.
Regards, Nadia
-- Nadia Derbey <Nadia.Derbey@bull.net>
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