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

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Date:	Sun, 12 Apr 2015 21:33:33 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] tcp/dccp: get rid of central timewait timer

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 10 Apr 2015 12:19:34 -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.
> 
> Tested:
 ...
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

First of all, I had to munge your commit message by hand.  All of
those ping output lines that start with '---' tell 'git am' "commit
message ends here" so most of your test results got removed.  I added
them back by hand.

Second of all, this doesn't compile:

net/ipv4/tcp_minisocks.c: In function ‘tcp_time_wait’:
net/ipv4/tcp_minisocks.c:283:27: warning: passing argument 2 of ‘inet_twsk_alloc’ from incompatible pointer type
  tw = inet_twsk_alloc(sk, &tcp_death_row.tw_count, state);
                           ^
In file included from include/linux/tcp.h:24:0,
                 from include/net/tcp.h:24,
                 from net/ipv4/tcp_minisocks.c:26:
include/net/inet_timewait_sock.h:108:28: note: expected ‘struct inet_timewait_death_row *’ but argument is of type ‘struct atomic_t *’
 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
                            ^