netdev - Re: [PATCH v2 net-next] tcp/dccp: get rid of central timewait timer

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Date:	Mon, 13 Apr 2015 16:40:50 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next] tcp/dccp: get rid of central timewait timer

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sun, 12 Apr 2015 18:51:09 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Using a timer wheel for timewait sockets was nice ~15 years ago when
> memory was expensive and machines had a single processor.
> 
> This does not scale, code is ugly and source of huge latencies
> (Typically 30 ms have been seen, cpus spinning on death_lock spinlock.)
> 
> We can afford to use an extra 64 bytes per timewait sock and spread
> timewait load to all cpus to have better behavior.
 ...
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---
>  v2: removed last inet_twsk_schedule() argument
>      restored original SNMP counters : TW / TWKill
>      fixed a compilation error reported by David
>      Removed the problematic --- markers from ping in changelog

Applied, but:

> @@ -367,115 +269,15 @@ void inet_twsk_schedule(struct inet_timewait_sock *tw,
>  	 * is greater than TS tick!) and detect old duplicates with help
>  	 * of PAWS.
>  	 */
> -	slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK;
>  
> -	spin_lock(&twdr->death_lock);
> -
> -	/* Unlink it, if it was scheduled */
> -	if (inet_twsk_del_dead_node(tw))
> -		twdr->tw_count--;
> -	else
> +	tw->tw_kill = timeo <= 4*HZ;	

That last line has trailing whitespace which I removed.
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