On 07/30/2011 02:12 AM, Badari Pulavarty wrote:
Hi Liu Yuan,
I am glad to see that you started looking at vhost-blk. I did an
attempt year ago to improve block
performance using vhost-blk approach.
http://lwn.net/Articles/379864/
http://lwn.net/Articles/382543/
I will take a closer look at your patchset to find differences and
similarities.
- I focused on using vfs interfaces in the kernel, so that I can use
it for file-backed devices.
Our use-case scenario is mostly file-backed images.
vhost-blk's that uses Linux AIO also support file-backed images.
Actually, I have run Guests both on raw partition and raw file images.
- In few cases, virtio-blk did outperform vhost-blk -- which was
counter intuitive - but
couldn't exactly nail down. why ?
- I had to implement my own threads for parellism. I see that you are
using aio infrastructure
to get around it.
- In our high scale performance testing, what we found is block-backed
device performance is
pretty close to bare-metal (91% of bare-metal). vhost-blk didn't add
any major benefits to it.
I am curious on your performance analysis & data on where you see the
gains and why ?
Possibly bypass vfs-layer and translate sg lists from virtio buffer into
BIOs would benefit the block-backed device. I'll give it a try later.
Hence I prioritized my work low :(
Now that you are interested in driving this, I am happy to work with
you and see what
vhost-blk brings to the tables. (even if helps us improve virtio-blk).
Thanks,
Badari
That's great.
Yuan
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