netdev - Re: [patch net-next] virtio_net: add support for Byte Queue Limits

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Date: Thu, 16 May 2024 15:04:41 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jiri Pirko <jiri@...nulli.us>
Cc: Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, xuanzhuo@...ux.alibaba.com,
	virtualization@...ts.linux.dev, ast@...nel.org,
	daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com
Subject: Re: [patch net-next] virtio_net: add support for Byte Queue Limits

On Thu, May 16, 2024 at 05:25:20PM +0200, Jiri Pirko wrote:
> 
> >I'd expect a regression if any to be in a streaming benchmark.
> 
> Can you elaborate?

BQL does two things that can hurt throughput:
- limits amount of data in the queue - can limit bandwidth
  if we now get queue underruns
- adds CPU overhead - can limit bandwidth if CPU bound

So checking result of a streaming benchmark seems important.


-- 
MST