netdev - Re: [PATCH net-next] sch_netem: faster rb tree removal

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Date:   Sun, 24 Sep 2017 22:27:20 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [PATCH net-next] sch_netem: faster rb tree removal

On Sun, 2017-09-24 at 20:05 -0600, David Ahern wrote:
> On 9/24/17 7:57 PM, David Ahern wrote:

> > Hi Eric:
> > 
> > I'm guessing the cost is in the rb_first and rb_next computations. Did
> > you consider something like this:
> > 
> >         struct rb_root *root
> >         struct rb_node **p = &root->rb_node;
> > 
> >         while (*p != NULL) {
> >                 struct foobar *fb;
> > 
> >                 fb = container_of(*p, struct foobar, rb_node);
> >                 // fb processing
> 		  rb_erase(&nh->rb_node, root);
> 
> >                 p = &root->rb_node;
> >         }
> > 
> 
> Oops, dropped the rb_erase in my consolidating the code to this snippet.

Hi David

This gives about same numbers than method_1

I tried with 10^7 skbs in the tree :

Your suggestion takes 66ns per skb, while the one I chose takes 37ns per
skb.

Thanks.