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

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Date:   Mon, 25 Sep 2017 09:52:01 -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 Mon, 2017-09-25 at 10:14 -0600, David Ahern wrote:

> Thanks for the test.
> 
> I made a simple program this morning and ran it under perf. With the
> above suggestion the rb_erase has a high cost because it always deletes
> the root node. Your method 1 has a high cost on rb_first which is
> expected given its definition and it is run on each removal. Both
> options increase in time with the number of entries in the tree.
> 
> Your method 2 is fairly constant from 10,000 entries to 10M entries
> which makes sense: a one time cost at finding rb_first and then always
> removing a bottom node so rb_erase is light.
> 
> As for the change:
> 
> Acked-by: David Ahern <dsahern@...il.com>

Thanks a lot for double checking !