netdev - Re: Scalability of interface creation and deletion

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Date:	Sat, 07 May 2011 18:51:05 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ben Greear <greearb@...delatech.com>
Cc:	Alex Bligh <alex@...x.org.uk>, netdev@...r.kernel.org
Subject: Re: Scalability of interface creation and deletion

Le samedi 07 mai 2011 à 09:44 -0700, Ben Greear a écrit :
> On 05/07/2011 09:37 AM, Eric Dumazet wrote:
> > Le samedi 07 mai 2011 à 09:23 -0700, Ben Greear a écrit :
> >
> >> I wonder if it would be worth having a 'delete me soon'
> >> method to delete interfaces that would not block on the
> >> RCU code.
> >>
> >> The controlling programs could use netlink messages to
> >> know exactly when an interface was truly gone.
> >>
> >> That should allow some batching in the sync-net logic
> >> too, if user-space code deletes 1000 interfaces very
> >> quickly, for instance...
> >>
> >
> > I suggested in the past to have an extension of batch capabilities, so
> > that one kthread could have 3 separate lists of devices being destroyed
> > in //,
> >
> > This daemon would basically loop on one call to synchronize_rcu(), and
> > transfert list3 to deletion, list2 to list3, list1 to list2, loop,
> > eventually releasing RTNL while blocked in synchronize_rcu()
> >
> > This would need to allow as you suggest an asynchronous deletion method,
> > or use a callback to wake the process blocked on device delete.
> 
> I'd want to at least have the option to not block the calling
> process...otherwise, it would be a lot more difficult to
> quickly delete 1000 interfaces.  You'd need 1000 threads, or
> sockets, or something to parallelize it otherwise, eh?

Yes, if you can afford not receive a final notification of device being
fully freed, it should be possible.


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