linux-kernel - Re: A quick fio test (was Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3)

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Message-ID: <45E45915.20204@argo.co.il>
Date:	Tue, 27 Feb 2007 18:15:17 +0200
From:	Avi Kivity <avi@...o.co.il>
To:	Ingo Molnar <mingo@...e.hu>
CC:	suparna@...ibm.com, Jens Axboe <jens.axboe@...cle.com>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@....com.au>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ulrich Drepper <drepper@...hat.com>,
	Zach Brown <zach.brown@...cle.com>,
	Evgeniy Polyakov <johnpol@....mipt.ru>,
	"David S. Miller" <davem@...emloft.net>,
	Davide Libenzi <davidel@...ilserver.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: A quick fio test (was Re: [patch 00/13] Syslets, "Threadlets",
 generic AIO support, v3)

Ingo Molnar wrote:
> * Avi Kivity <avi@...o.co.il> wrote:
>
>   
>> But what about cpu usage?  At these low levels, the cpu is probably 
>> underutilized.  It would be interesting to measure cpu time per I/O 
>> request (or, alternatively, use an I/O subsystem that can saturate the 
>> processors).
>>     
>
> yeah - that's what testing on ramdisk (Jens') or on a loopback block 
> device (mine) approximates to a certain degree.
>
>   

Ramdisks or fully cached loopback return immediately, so cache thrashing 
effects don't show up.

Maybe a device mapper delay target or nbd + O_DIRECT can insert delays 
to make the workload more disk-like.




-- 
error compiling committee.c: too many arguments to function

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