netdev - Re: [RFC][PATCH] iproute: Faster ip link add, set and delete

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Message-ID: <87ppyj6ohh.fsf@xmission.com>
Date:	Thu, 28 Mar 2013 17:25:46 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Stephen Hemminger <stephen@...workplumber.org>,
	Benoit Lourdelet <blourdel@...iper.net>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	"netdev\@vger.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [RFC][PATCH] iproute: Faster ip link add, set and delete

Eric Dumazet <eric.dumazet@...il.com> writes:

> On Thu, 2013-03-28 at 16:52 -0700, Eric W. Biederman wrote:
>
>> On my microbenchmark of just creating 5000 veth pairs this takes pairs
>> 16s instead of 13s of my earlier hacks but that is well down in the
>> usable range.
>
> I guess most of the time is taken by sysctl_check_table()

All of the significant sysctl slowdowns were fixed in 3.4.  If you see
something of sysctl show up in a trace I would be happy to talk about
it.  The kernel side seems to be creating N network devices seems to
take NlogN time now.  Both sysfs and sysctl store directories as
rbtrees removing their previous bottlenecks.

The loop I timed at 16s was just:

time for i in $(seq 1 5000) ; do ip link add a$i type veth peer name b$i; done

There is plenty of room for inefficiencies in 10000 network devices and
5000 forks+execs.

Eric

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