netdev - Re: [PATCH net-next 00/10] net_sched: defer skb freeing while changing qdiscs

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Date:	Wed, 15 Jun 2016 07:43:03 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	Eric Dumazet <edumazet@...gle.com>,
	"David S . Miller" <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	Cong Wang <xiyou.wangcong@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH net-next 00/10] net_sched: defer skb freeing while
 changing qdiscs

On 16-06-13 11:21 PM, Eric Dumazet wrote:
> qdiscs/classes are changed under RTNL protection and often
> while blocking BH and root qdisc spinlock.
>
> When lots of skbs need to be dropped, we free
> them under these locks causing TX/RX freezes,
> and more generally latency spikes.
>
> I saw spikes of 50+ ms on quite fast hardware...
>
> This patch series adds a simple queue protected by RTNL
> where skbs can be placed until RTNL is released.
>
> Note that this might also serve in the future for optional
> reinjection of packets when a qdisc is replaced.
>

Nice optimization Eric.

cheers,
jamal