Re: [RFC PATCH 1/1] vhost: TX used buffer guest signal accumulation

Shirley Ma
2010-10-28T19:32:35Z

On Thu, 2010-10-28 at 07:20 +0200, Michael S. Tsirkin wrote:
> My concern is this can delay signalling for unlimited time.
> Could you pls test this with guests that do not have
> 2b5bbe3b8bee8b38bdc27dd9c0270829b6eb7eeb
> b0c39dbdc204006ef3558a66716ff09797619778
> that is 2.6.31 and older?

The patch only induces delay signaling unlimited time when there is no
TX packet to transmit. I thought TX signaling only noticing guest to
release the used buffers, anything else beside this?

I tested rhel5u5 guest (2.6.18 kernel), it works fine. I checked the two
commits log, I don't think this patch could cause any issue w/o these
two patches.

Also I found a big TX regression for old guest and new guest. For old
guest, I am able to get almost 11Gb/s for 2K message size, but for the
new guest kernel, I can only get 3.5 Gb/s with the patch and same host.
I will dig it why.

thanks
Shirley