Subject: Re: [PATCH] sky2: skb recycling

From: Eric Dumazet <[email-masked]>
Date: Tue, 21 Oct 2008 14:42:37 +0200

Robert Olsson a écrit :
> Terry writes:
>  > Hi 
>  >     yeah. In the forwarding scenario , skb recycling should boost the 
>  > performance by avoiding slowpath slub alloc/free .But if  using 
>  > multiqueue hardware and assigning proper  cpu affinities  could  make it 
>  > always in the fastpath of slub  alloc/free, which is faster?
> 
>  For perfect setup with monotone work like forwarding you can make the skb 
>  recycling a little faster.
> 
>  If you have many active NIC's and the recycling list is per device the situation
>  it's probably different...
> 

I suspect all this skb recycling stuff in forwarding workloads is defeated anyway...

By the copybreak feature... (RX_COPY_THRESHOLD = 256 for example on tg3)

Checking drivers/net/tg3.c, we can even see that in case of copying to a smaller skb,
we allocate it with a call to netdev_alloc_skb(), while it would be better
to use a plain alloc_skb() ...