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From: Jens Axboe <>
To: Davide Libenzi <>
Cc: Linux Kernel Mailing List <>,
	Ingo Molnar <>,
	Linus Torvalds <>
Subject: Re: AIO, FIO and Threads ...
Date: Wed, 21 Mar 2007 08:40:14 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, Mar 20 2007, Davide Libenzi wrote:
> I was looking at Jens FIO stuff, and I decided to cook a quick patch for 
> FIO to support GUASI (Generic Userspace Asyncronous Syscall Interface):
> I then ran a few tests on my Dual Opteron 252 with SATA drives (sata_nv) 
> and 8GB of RAM.
> Mind that I'm not FIO expert, like at all, but I got some interesting 
> results when comparing GUASI with libaio at 8/1000/10000 depths.
> If I read those result correctly (Jens may help), GUASI output is more 
> then double the libaio one.
> Lots of context switches, yes. But the throughput looks like 2+ times.
> Can someone try to repeat the measures and/or spot the error?
> Or tell me which other tests to run?
> This is kinda a suprise for me ...

I don't know guasi at all, but libaio requires O_DIRECT to be async. I'm
sure you know this, but you may not know that fio default to buffered IO
so you have to tell it to use O_DIRECT :-)

So try adding a --direct=1 (or --buffered=0, same thing) as an extra
option when comparing depths > 1.

I'll add your guasi engine, but disable it. Unfortunately fio still
doesn't have a nifty configure setup, so these things are still

Jens Axboe

  parent reply	other threads:[~2007-03-21  7:41 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-03-21  4:58 Davide Libenzi
2007-03-21  6:54 ` Davide Libenzi
2007-03-21  7:40 ` Jens Axboe [this message]
2007-03-21 15:23   ` Davide Libenzi
2007-03-22  6:47     ` Jens Axboe
2007-03-22  2:02   ` Davide Libenzi

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