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

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Message-Id: <20151129.223110.1579432138646337508.davem@davemloft.net>
Date:	Sun, 29 Nov 2015 22:31:10 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	jasowang@...hat.com
Cc:	mst@...hat.com, kvm@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 0/3] basic busy polling support for vhost_net

From: Jason Wang <jasowang@...hat.com>
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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