Thanks Duncan for reproducing the behavior outside myself and Phoronix.
I dug deeper into the actual syscalls being made by sqlite. The salient
part of the behaviour is small sequential writes followed by a fdatasync
(effectively a metadata-free fsync).
As Dustin indicates,
if scsi is used, you incur the cost of virtualization,
if virtio is used, your guests fsyncs incur less cost.
So back to the question to the kvm team. It appears that with the stock
KVM setup customers who need higher data integrity (through fsync)
should steer away from virtio for the moment.
Is that assessment correct?
Regards,
Matthew
-------- Original Message --------
Subject: Re: sync guest calls made async on host - SQLite performance
From: Dustin Kirkland <dustin.kirkland@xxxxxxxxx>
To: Matthew Tippett <tippettm@xxxxxxxxx>, Anthony Liguori
<anthony@xxxxxxxxxxxxx>, Avi Kivity <avi@xxxxxxxxxx>, RW
<kvm@xxxxxxxxxxx>, kvm@xxxxxxxxxxxxxxx
Date: 10/09/2009 11:18 AM
On Fri, Oct 9, 2009 at 6:25 AM, Matthew Tippett <tippettm@xxxxxxxxx> wrote:
Can I ask you to do the following...
1) Re-affirm that Ubuntu does not carry any non-stream patches and
the build command and possibly any other unusual patches or
commandline options. This should push it back onto Avi and Anthony's
plate.
I have put the patches we're carrying here, for your review:
* http://rookery.canonical.com/~kirkland/patches
There's nothing exotic in here. Most of these have been committed
upstream already. All of them have been at least posted on these
lists. None of these should affect your test case.
We configure with:
./configure --prefix=/usr --disable-blobs --audio-drv-list="alsa pa
oss sdl" --audio-card-list="ac97 es1370 sb16 cs4231a adlib gus"
--target-list="$(TARGET_SYSTEM_TCG) $(TARGET_LINUX_TCG)"
We carry a number of compiler options, mostly in the interest of
hardening and security:
* https://wiki.ubuntu.com/CompilerFlags
The #define'd variables on my local system (which should be similar,
though not identical to our build servers) can be seen here:
* http://rookery.canonical.com/~kirkland/defined
2) Carefully consider risks to virtualized environments in the
server space and consider noting it in release notes.
Thank you for the suggestion. I will take it under consideration.
:-Dustin
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