netdev - Re: Scalability of interface creation and deletion

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Message-ID: <1304785589.3207.5.camel@edumazet-laptop>
Date:	Sat, 07 May 2011 18:26:29 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Alex Bligh <alex@...x.org.uk>
Cc:	netdev@...r.kernel.org
Subject: Re: Scalability of interface creation and deletion

Le samedi 07 mai 2011 à 16:26 +0100, Alex Bligh a écrit :

> On the current 8 core box I am testing, I see 280ms per interface
> delete **even with only 10 interfaces**. I see 260ms with one
> interface. I know doing lots of rcu sync stuff can be slow, but
> 260ms to remove one veth pair sounds like more than rcu sync going
> on. It sounds like a sleep (though I may not have found the
> right one). I see no CPU load.
> 

Here, on 2.6.38 kernel (Ubuntu 11.04 provided, on my 2 core laptop)

# time rmmod dummy

real	0m0.111s
user	0m0.000s
sys	0m0.000s


This removed my two dummy0/dummy1 devices.

On another machine with a very recent kernel :
$ modprobe dummy numdummies=1
$ ifconfig dummy0 192.168.46.46 up
$ time rmmod dummy

real	0m0.032s
user	0m0.000s
sys	0m0.001s
$ uname -a
Linux svivoipvnx001 2.6.39-rc6-00097-g6ac1576-dirty #550 SMP Sat May 7
00:12:26 CEST 2011 i686 i686 i386 GNU/Linux


So 260ms is a bit too much, maybe you hit yet another bug.




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