netdev - Re: Scalability of interface creation and deletion

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Date:	Sat, 07 May 2011 20:45:07 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Alex Bligh <alex@...x.org.uk>, netdev@...r.kernel.org
Subject: Re: Scalability of interface creation and deletion

On 05/07/2011 09:51 AM, Eric Dumazet wrote:
> 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.

Well, I'd hope to get a netlink message about the device being deleted, and
after that, be able to create another one with the same name, etc.

Whether the memory is actually freed in the kernel or not wouldn't matter
to me...

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com
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