linux-kernel - Re: Scalability requirements for sysv ipc

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Date:	Sun, 23 Mar 2008 07:38:42 +0100
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Mike Galbraith <efault@....de>
CC:	paulmck@...ux.vnet.ibm.com, Nadia Derbey <Nadia.Derbey@...l.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Scalability requirements for sysv ipc

Mike Galbraith wrote:
> On Sat, 2008-03-22 at 15:22 +0100, Manfred Spraul wrote:
>   
>> Mike Galbraith wrote:
>>     
>>> Total: 4691827                                Total: 3942000
>>>   
>>>       
>> Thanks. Unfortunately the test was buggy, it bound the tasks to the 
>> wrong cpu :-(
>> Could you run it again? Actually 1 cpu and 4 cpus are probably enough.
>>     
>
> Sure.  (ran as before, hopefully no transcription errors)
>
>   
Thanks:
sysv sem:
- 2.6.22 had almost linear scaling (up to 4 cores).
- 2.6.24.3 scales to 2 cpus, then it collapses. with 4 cores, it's 75% 
slower than 2.6.22.

sysv msg:
- neither 2.6.22 nor 2.6.24 scale very good. That's more or less 
expected, the message queue code contains a few global statistic 
counters (msg_hdrs, msg_bytes).

The cleanup of sysv is nice, but IMHO sysv sem should remain scalable - 
and a gloal semaphore with IDR can't be as scalable as the RCU protected 
array that was used before.

--
    Manfred
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