linux-kernel - Re: [RFC -mm 0/6] sysv ipc: scale msgmnb with the number of cpus

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Date:	Mon, 23 Jun 2008 15:15:12 +0200
From:	Solofo.Ramangalahy@...l.net
To:	Manfred Spraul <manfred@...orfullife.com>
Cc:	Solofo.Ramangalahy@...l.net, linux-kernel@...r.kernel.org,
	Matt Helsley <matthltc@...ibm.com>,
	Mingming Cao <cmm@...ibm.com>,
	Nadia Derbey <Nadia.Derbey@...l.net>,
	Yasunori Goto <y-goto@...fujitsu.com>
Subject: Re: [RFC -mm 0/6] sysv ipc: scale msgmnb with the number of cpus

Hi Manfred,

This part is more difficult to answer than the other one:
> The whole configuration can be done from user space, thus I assumed that
> a sysctl.conf value [...] could do the job

Yes, while this is (still) possible, this can become cumbersome with
namespaces, hotplug, ...

> (or in the worst case: a dbus/hal daemon that
> updates /proc/sys/kernel/msgnmb) [...]

This would probably mean one daemon per ipc namespace.
The patches seems lighter.

There has been related discussions regarding kernel
space vs. userspace approach in the threads:
. "Change in default vm_dirty_ratio"
  http://lkml.org/lkml/2007/6/18/471
. "[RFC][PATCH 0/6] Automatic kernel tunables (AKT)"
  http://lkml.org/lkml/2007/1/16/16
(and probably others)

So it seems there is no consensus in doing it either way: kernel or
user space.

Humm... now this make me think that you did not change the MSGMNB
value when you changed MSGMNI and MSGMAX.
Maybe that was on purpose?

-- 
solofo
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