Re: [PATCH net-next 0/3] basic busy polling support for vhost_net

From: David Miller
Date: Sun Nov 29 2015 - 22:31:18 EST

From: Jason Wang <jasowang@xxxxxxxxxx>
Date: Wed, 25 Nov 2015 15:11:26 +0800

> This series tries to add basic busy polling for vhost net. The idea is
> simple: at the end of tx/rx processing, busy polling for new tx added
> descriptor and rx receive socket for a while. The maximum number of
> time (in us) could be spent on busy polling was specified ioctl.
> Test A were done through:
> - 50 us as busy loop timeout
> - Netperf 2.6
> - Two machines with back to back connected ixgbe
> - Guest with 1 vcpu and 1 queue
> Results:
> - For stream workload, ioexits were reduced dramatically in medium
> size (1024-2048) of tx (at most -43%) and almost all rx (at most
> -84%) as a result of polling. This compensate for the possible
> wasted cpu cycles more or less. That porbably why we can still see
> some increasing in the normalized throughput in some cases.
> - Throughput of tx were increased (at most 50%) expect for the huge
> write (16384). And we can send more packets in the case (+tpkts were
> increased).
> - Very minor rx regression in some cases.
> - Improvemnt on TCP_RR (at most 17%).

Michael are you going to take this? It's touching vhost core as
much as it is the vhost_net driver.
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