Re: [PATCH net-next] tuntap: introduce tx skb ring

[Michael S. Tsirkin]

On Wed, May 18, 2016 at 10:16:31AM +0200, Jesper Dangaard Brouer wrote:
> 
> On Tue, 17 May 2016 09:38:37 +0800 Jason Wang <jasowang@xxxxxxxxxx> wrote:
> 
> > >> And if tx_queue_length is not power of 2,
> > >> we probably need modulus to calculate the capacity.  
> > > Is that really that important for speed?  
> > 
> > Not sure, I can test.
> 
> In my experience, yes, adding a modulus does affect performance.

How about simple
	if (unlikely(++idx > size))
		idx = 0;


> > 
> > Right, this sounds a good solution.
> 
> Good idea.

I'm not that sure - it's clearly wasting memory.

> -- 
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Principal Kernel Engineer at Red Hat
>   Author of http://www.iptv-analyzer.org
>   LinkedIn: http://www.linkedin.com/in/brouer