From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: sync guest calls made async on host - SQLite performance
Date: Wed, 07 Oct 2009 22:12:19 +0200
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Cc: Dustin Kirkland <dustin.kirkland@gmail.com>,
	Anthony Liguori <anthony@codemonkey.ws>, RW <kvm@tauceti.net>,
	kvm@vger.kernel.org
To: Matthew Tippett <tippettm@gmail.com>
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On 10/07/2009 09:31 PM, Matthew Tippett wrote:
> The benchmark used was the sqlite subtest in the phoronix test suite.
>
> My awareness and involvement is beyond "reading a magazine article", I 
> can elaborate if needed, but I don't believe it is necessary.
>
> Process for reproduction, assuming Karmic,
>
>     # apt-get install phoronix-test-suite
>
>         $ phoronix-test-suite benchmark sqlite
>
> Answer the questions (test-names, etc, etc), it will download sqlite, 
> build it and execute the test.  By default the test runs three 
> timesand averages the results.  The results experienced should be 
> similar to the values identified at
>
> http://www.phoronix.com/scan.php?page=article&item=linux_2631_kvm&num=3
>
> Which is approximately 12 minutes for the native, and about 60 seconds 
> for the guest.
>
> Given that the performance under the guest is expected to be around 60 
> seconds, I would suggest confirming performance there first.

What is the data set for this benchmark?  If it's much larger than guest 
RAM, but smaller than host RAM, you could be seeing the effects of read 
caching.

Another possiblity is barriers and flushing.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.