linux-kernel - Re: [PATCH 0/4] ipc/sem.c: Bug fixes, regression fixes, v3

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Date:	Mon, 27 May 2013 17:57:11 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Davidlohr Bueso <davidlohr.bueso@...com>
CC:	Rik van Riel <riel@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, hhuang@...hat.com,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 0/4] ipc/sem.c: Bug fixes, regression fixes, v3

Hi Davidlohr,

On 05/26/2013 10:50 PM, Davidlohr Bueso wrote:
>
> In lack of getting my swingbench DSS environment back, I ran these
> changes against the semop-multi program on my laptop. For 256 threads,
> with Manfred's patchset the ops/sec suffers around -7.3%.

Could you also check the performance of only patch#1?
I fear that it might be slower than all 4 together.

With regards to semop-multi:
Is this the tool?
http://marc.info/?l=linux-kernel&m=136208613626892&q=p3

I think the logic is the wrong:
Locking a semaphore is substraction, unlocking adding.
Thus multiple tasks can run in parallel - and the task switch code is 
never triggered.
Could you double check that the number of context switches matches the 
output?

I usually use this tool:
http://marc.info/?l=linux-kernel&m=125038376609750

--
     Manfred
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