linux-kernel - Re: [PATCH -mm v2 3/3] sysv ipc: use auto_msgmnb to desactivate and reactivate msgmnb recomputation

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Message-Id: <20080717141409.2edcb7be.rdunlap@xenotime.net>
Date:	Thu, 17 Jul 2008 14:14:09 -0700
From:	Randy Dunlap <rdunlap@...otime.net>
To:	<Solofo.Ramangalahy@...l.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>, Matt Helsley <matthltc@...ibm.com>,
	Mingming Cao <cmm@...ibm.com>,
	Nadia Derbey <Nadia.Derbey@...l.net>,
	Manfred Spraul <manfred@...orfullife.com>
Subject: Re: [PATCH -mm v2 3/3] sysv ipc: use auto_msgmnb to desactivate and
 reactivate msgmnb recomputation

On Tue, 15 Jul 2008 23:14:10 +0200 Solofo.Ramangalahy@...l.net wrote:

> From: Solofo Ramangalahy <Solofo.Ramangalahy@...l.net>
> 
> Add /proc/sys/kernel/auto_msgmnb to control automatic recomputation of
> /proc/sys/kernel/msgmnb (msg_ctlmnb).
> 
> Signed-off-by: Solofo Ramangalahy <Solofo.Ramangalahy@...l.net>
> ---
>  Documentation/sysctl/kernel.txt |   35 ++++++++++++++++
>  include/linux/ipc_namespace.h   |    5 ++
>  ipc/ipc_sysctl.c                |   87 ++++++++++++++++++++++++++++++++++++----
>  ipc/ipcns_notifier.c            |   62 +++++++++++++++++++++++++++-
>  ipc/namespace.c                 |    2 
>  ipc/util.c                      |    1 
>  6 files changed, 183 insertions(+), 9 deletions(-)
> 
> Index: linux-2.6.26-rc8-mm1-MSGMNB3/Documentation/sysctl/kernel.txt
> ===================================================================
> --- linux-2.6.26-rc8-mm1-MSGMNB3.orig/Documentation/sysctl/kernel.txt
> +++ linux-2.6.26-rc8-mm1-MSGMNB3/Documentation/sysctl/kernel.txt
> @@ -179,6 +179,41 @@ kernel stack.
>  
>  ==============================================================
>  
> +msgmnb
> +
> +Maximum size in bytes, not in message count, of a single SystemV IPC
> +message queue (b stands for bytes).
> +
> +This value is dynamic and depends on the online cpu count of the
> +machine (taking cpu hotplug into account).

Prefer "CPU" to "cpu".

> +
> +Computed values are between MSGMNB and MSGMNB*MSG_CPU_SCALE #define
> +constants (currently [16384,65536]).
> +
> +The exact value is automatically (re)computed, but:
> +
> +. If the value is positioned from user space (via procfs or sysctl()),

s/positioned/specified/ or set

> +  then the automatic recomputation is disabled. E.g.:
> +
> +  # echo 16384 > /proc/sys/kernel/msgmnb
> +
> +. The automatic recomputation can also be disabled via auto_msgmnb,
> +  e.g.:
> +
> +  # echo 0 > /proc/sys/kernel/auto_msgmnb
> +
> +. When disabled, the automatic recomputation can be reenabled via
> +  auto_msgmnb, e.g.:
> +
> +  # echo 1 > /proc/sys/kernel/auto_msgmnb
> +
> +The msgmnb and auto_msgmnb values in each (ipc) namespace are
> +independent.
> +

Prefer IPC instead of ipc (above and below).

> +Initially, the msgmnb value is computed automatically: at boot time
> +and (ipc) namespace creation.
> +
> +==============================================================


---
~Randy
Linux Plumbers Conference, 17-19 September 2008, Portland, Oregon USA
http://linuxplumbersconf.org/
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