netdev - Re: [PATCH net-next 0/4] batch calls to fib_flush and arp

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Message-ID: <CAO7SqHA6f8LT6OvsoDj0nd-+W0VxuKT+bL86QAy_oFtVSW=mgw@mail.gmail.com>
Date:	Mon, 11 Jan 2016 17:53:16 -0800
From:	Salam Noureddine <noureddine@...sta.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jiri Pirko <jiri@...lanox.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 0/4] batch calls to fib_flush and arp_ifdown

Any thoughts on the correctness of the patchset? Or a different way to
solve this issue leading to long rtnl_lock hold time?

Thanks,

Salam

On Mon, Jan 4, 2016 at 5:12 PM, Salam Noureddine <noureddine@...sta.com> wrote:
> On Mon, Jan 4, 2016 at 4:35 PM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
>
>> Two things would be very valuable with this patchset.
>>
>> Some numbers on how much your changes have improved the code in the case
>> you care about.  I suspect the improvements are not subtle so this
>> should not be hard.
>>
>> Can you please provide a justification for event_list.  Just skimming
>> through it appears that event_list because a duplicate of the list of
>> batched network devices that are passed to dev_close_many and friends.
>> If the list is actually a duplicate it appears foolish to create it.
>>
>> Eric
>
> The performance test I ran tries to unregister 1000 dummy interfaces
> with 512K routes in the fib.
> Without the patch I could unregister 35 interfaces per second and with
> the patch it jumped to 620
> interfaces per second. 512K is a lot of routes but I am assuming we
> would get a good improvement
> even with 100K routes in the fib.
>
> I am using event_list to put all the net namespaces in the current
> net_device batch on a list and only
> call the NETDEV_UNREGISTER_BATCH on those namespaces. It would be
> possible to just call the
> notifier for NETDEV_DOWN/UNREGISTER_BATCH for all the devices on the
> list and rely on the
> needs_fib_flush flag to only call fib_flush once per namespace but it
> seems like a waste to me.
>
> Salam