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From: Jeff Garzik <jeff@garzik.org>
To: Francis Moreau <francis.moro@gmail.com>
Cc: linux-kernel@vger.kernel.org, jens.axboe@oracle.com
Subject: Re: question about splice performance
Date: Sun, 25 May 2008 16:47:24 -0400	[thread overview]
Message-ID: <4839D05C.4040309@garzik.org> (raw)
In-Reply-To: <38b2ab8a0805250812l2ecd424bh74a1694ed56460de@mail.gmail.com>

Francis Moreau wrote:
> Hi,
> 
> I did a really basic benchmark and was suprise about the results.
> 
> $ echo 3 > /proc/sys/vm/drop_caches
> $ time  splice-cp  vmlinux /tmp/vmlinux
> 
> real    0m10.158s
> user    0m0.002s
> sys     0m0.401s
> 
> $ echo 3 > /proc/sys/vm/drop_caches
> $ time  cp  vmlinux /tmp/vmlinux
> 
> real    0m10.590s
> user    0m0.017s
> sys     0m0.459s
> 
> 
> I was expecting splice-cp case to be faster.
> 
> Could someone enlight me ?

If you drop caches you are not measuring splice speed.

Use ramfs for your tests (guarantees data is in cache) instead.

	Jeff




  parent reply	other threads:[~2008-05-25 20:47 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-05-25 15:12 question about splice performance Francis Moreau
2008-05-25 15:40 ` Jan Engelhardt
2008-05-25 17:22 ` Sitsofe Wheeler
2008-05-25 20:47 ` Jeff Garzik [this message]
2008-05-26  8:57   ` Francis Moreau
2008-05-26  9:06     ` Bernd Petrovitsch

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