Re: [PATCH] kvm:virtio-net: Run TX from the I/O thread

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Mark McLoughlin wrote:
Hi Alex,

On Wed, 2009-01-21 at 16:08 -0700, Alex Williamson wrote:
This is an attempt to improve the latency of virtio-net while not hurting
throughput.  I wanted to try moving packet TX into a different thread
so we can quickly return to the guest after it kicks us to send packets
out.  I also switched the order of when the tx_timer comes into play, so
we can get an inital burst of packets out, then wait for the timer to
fire and notify us if there's more to do.  Here's what it does for me
(average of 5 runs each, testing to a remote system on a 1Gb network):

netperf TCP_STREAM: 939.22Mb/s -> 935.24Mb/s =  99.58%
netperf TCP_RR:      2028.72/s -> 3927.99/s  = 193.62%
tbench:              92.99MB/s -> 99.97MB/s  = 107.51%

I'd be interested to hear if it helps or hurts anyone else.  Thanks,

Avi and I went back and forth on this one in great detail before:

  http://www.mail-archive.com/kvm@xxxxxxxxxxxxxxx/msg06431.html

Avi's arguments make a lot of sense, but looking over those patches
again now, I still think that applying them would be a better approach
than what we have right now.

I can go with that. Anthony, should I wait for a qemu iothread so it can go upstream directly?

--
error compiling committee.c: too many arguments to function

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