netdev - Re: [PATCH net-next-2.6] net: speedup udp receive path

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Message-Id: <20100428.143610.232922250.davem@davemloft.net>
Date:	Wed, 28 Apr 2010 14:36:10 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	hadi@...erus.ca, xiaosuo@...il.com, therbert@...gle.com,
	shemminger@...tta.com, netdev@...r.kernel.org, eilong@...adcom.com,
	bmb@...enacr.com
Subject: Re: [PATCH net-next-2.6] net: speedup udp receive path

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Wed, 28 Apr 2010 16:06:45 +0200

> [PATCH net-next-2.6] net: speedup udp receive path
> 
> Since commit 95766fff ([UDP]: Add memory accounting.), 
> each received packet needs one extra sock_lock()/sock_release() pair.
> 
> This added latency because of possible backlog handling. Then later,
> ticket spinlocks added yet another latency source in case of DDOS.
> 
> This patch introduces lock_sock_bh() and unlock_sock_bh()
> synchronization primitives, avoiding one atomic operation and backlog
> processing.
> 
> skb_free_datagram_locked() uses them instead of full blown
> lock_sock()/release_sock(). skb is orphaned inside locked section for
> proper socket memory reclaim, and finally freed outside of it.
> 
> UDP receive path now take the socket spinlock only once.
> 
> Signed-off-by: Eric DUmazet <eric.dumazet@...il.com>

Clever, let's see what this breaks :-)

Applied, thanks Eric.
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