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Re: [Qemu-devel] Make virtio-net.c ring size configurable?

From: xchenum
Subject: Re: [Qemu-devel] Make virtio-net.c ring size configurable?
Date: Thu, 12 May 2016 10:38:05 -0700 (PDT)

Luke, I might have a similar problem... I am wondering if you end up 
increasing the ring buffer size yourself.

My problem is on the tx side. When sending many small udp packets, I am 
seeing "outgoing packets dropped" in "netstat -s" increase quickly. 
Increasing txqueue of the interface and wmem size in sysctl doesn't seem to 
help at all. tx ring size is what I am looking at now. My VM however is 
connected to a bridge and then to OpenVSwitch - so I might have other 


On Friday, February 14, 2014 at 8:43:14 AM UTC-5, Luke Gorrie wrote:
> Howdy!
> Observation: virtio-net.c hard-codes the vring size to 256 buffers.
> Could this reasonably be made configurable, or would that be likely to 
> cause a problem?
> In Snabb Switch we are creating a 1:1 mapping between Virtio-net 
> descriptors and VMDq hardware receive descriptors. The VMDq queues support 
> 32768 buffers and I'd like to match this on the QEMU/Virtio-net side -- or 
> at least come close.
> Cheers!
> -Luke

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