netdev - Re: [PATCH v2 net-next 1/1] net: netem: use a list in addition to rbtree

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Message-ID: <58785a0d-250d-ccab-4ec2-6c1cf03820a4@gmail.com>
Date:   Tue, 4 Dec 2018 12:09:51 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Peter Oskolkov <posk@...gle.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Cc:     Peter Oskolkov <posk.devel@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [PATCH v2 net-next 1/1] net: netem: use a list in addition to
 rbtree



On 12/04/2018 11:55 AM, Peter Oskolkov wrote:
> When testing high-bandwidth TCP streams with large windows,
> high latency, and low jitter, netem consumes a lot of CPU cycles
> doing rbtree rebalancing.
> 
> This patch uses a linear list/queue in addition to the rbtree:
> if an incoming packet is past the tail of the linear queue, it is
> added there, otherwise it is inserted into the rbtree.
> 
> Without this patch, perf shows netem_enqueue, netem_dequeue,
> and rb_* functions among the top offenders. With this patch,
> only netem_enqueue is noticeable if jitter is low/absent.
> 
> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Peter Oskolkov <posk@...gle.com>
> ---

Reviewed-by: Eric Dumazet <edumazet@...gle.com>