Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33

[Chris Wright]

* Anthony Liguori (anthony@xxxxxxxxxxxxx) wrote:
> The "poor" packet latency of virtio-net is a result of the fact that we  
> do software timer based TX mitigation.  We do this such that we can  
> decrease the number of exits per-packet and increase throughput.  We set  
> a timer for 250ms and per-packet latency will be at least that much.

Actually that's 150us ;-)  It's the AlacrityVM numbers that show 250us
(note micro, not milli) for latency.  That makes sense, shave off 150us
for the timer and you're left w/ 100us, which is not substantially
slower than what we see (for that bare metal latency we see ~60us)
when we switched tx mitigation schemes from timer based to thread
scheduling.  Quite similar to the 56.8us that vbus/venet shows.

thanks,
-chris
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