linux-kernel - Improving IPMI performance under load

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Message-ID: <49C8A823.6020809@fujitsu-siemens.com>
Date:	Tue, 24 Mar 2009 10:30:11 +0100
From:	Martin Wilck <martin.wilck@...itsu-siemens.com>
To:	Corey Minyard <minyard@....org>
CC:	Greg KH <greg@...ah.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"openipmi-developer@...ts.sourceforge.net" 
	<openipmi-developer@...ts.sourceforge.net>
Subject: Improving IPMI performance under load

Hi Corey,

yesterday I posted some results about the IPMI performance under CPU 
load, which can be up to 25 times slower than in an idle system. I think 
it might be worthwhile to try to improve that behavior as well.

I made a variation of my patch which introduces a second parameter 
(kipmid_min_busy) that causes kipmid not to call schedule() for a 
certain amount of time. Thus if there's IPMI traffic pending, kipmid 
will busy-loop for kipmid_min_busy seconds, then starting to schedule() 
in each loop as it does now, and finally go to sleep when 
kipmid_max_busy is reached. At the same time, I changed the nice value 
of kipmid from 19 to 0.

With this patch and e.g. min_busy=100 and max_busy=200, there is no 
noticeable difference any more between IPMI performance with and without 
CPU load.

The patch + results still need cleanup, therefore I am not sending it 
right now. Just wanted to hear what you think.

Martin

-- 
Martin Wilck
PRIMERGY System Software Engineer
FSC IP ESP DEV 6

Fujitsu Siemens Computers GmbH
Heinz-Nixdorf-Ring 1
33106 Paderborn
Germany

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