Re: vhost-blk development

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On Wed, Apr 11, 2012 at 5:52 PM, Michael Baysek <mbaysek@xxxxxxxxxxxxx> wrote:
> I am purposefully not using O_DIRECT since most workloads will not be using
> it, although I did notice better performance when I did use it.  I did
> already identify the page cache as a hinderance as well.

If you do not use O_DIRECT in the benchmark then you are not
exercising pure disk I/O and therefore the benchmark is not measuring
virtio-blk performance.

> I seem to have hit some performance ceilings inside of the kvm guests that
> are much lower than that of the host they are running on.  I am seeing a
> lot more interrupts and context switches on the parent than I am in the
> guests, and I am looking for any and all ways to cut these down.

If you don't care about persistence of data I suggest doing the
ramdisk or tmpfs inside the guest.  That way you keep all "storage"
operations inside the guest and avoid going through any storage
interface (virtio-blk, IDE, etc).  You should be able to achieve
maximum performance using this approach although it does require guest
configuration.

Hope this helps,

Stefan
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