netdev - Re: [PATCH net-next-2.6] net: sock_def_readable() and friends RCU conversion

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Message-ID: <1272697367.2230.106.camel@edumazet-laptop>
Date:	Sat, 01 May 2010 09:02:47 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
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: sock_def_readable() and friends RCU
 conversion

Le vendredi 30 avril 2010 à 16:35 -0700, David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Thu, 29 Apr 2010 23:01:49 +0200
> 
> > [PATCH net-next-2.6] net: sock_def_readable() and friends RCU conversion
> 
> So what's the difference between call_rcu() freeing this little waitqueue
> struct and doing it for the entire socket?
> 
> We'll still be doing an RCU call every socket destroy, and now we also have
> a new memory allocation/free per connection.
> 
> This has to show up in things like 'lat_connect' and friends, does it not?

Before patch :

lat_connect -N 10 127.0.0.1
TCP/IP connection cost to 127.0.0.1: 27.8872 microseconds

After :

lat_connect -N 10 127.0.0.1
TCP/IP connection cost to 127.0.0.1: 20.7681 microseconds

Strange isnt it ?

(special care should be taken with this bench, as it leave many sockets
in TIME_WAIT state, so to get consistent numbers we have to wait a while
before restarting it)



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