Subject: Re: regression: unregister_netdev() unusably slow

From: Eric Dumazet <[email-masked]>
Date: Sun, 24 May 2009 23:42:17 +0200

Benjamin LaHaise a écrit :
> On Mon, May 25, 2009 at 12:23:30AM +0300, Denys Fedoryschenko wrote:
>> Once oprofile gave me hint about similar issue
> 
> I forgot to mention: there is no more than ~1% CPU usage while the interfaces 
> are being deleted.  I'm about half way through the bisect now and should have 
> the culprit soon. 
> 
> 		-ben

unregister a vlan here cost about 100 ms if CONFIG_NO_HZ is set, 50 ms if not set

(But vlan case might be litle bit more expensive than your case, since we call
synchronize_net() three times (once in unregister_vlan_dev(), and twice in rollback_registered()