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

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Date:	Thu, 28 Mar 2013 17:43:57 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Stephen Hemminger <stephen@...workplumber.org>,
	Benoit Lourdelet <blourdel@...iper.net>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [RFC][PATCH] iproute: Faster ip link add, set and delete

On Thu, 2013-03-28 at 17:25 -0700, Eric W. Biederman wrote:
> 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.

Ah right, the sysctl part is fixed ;)

In batch mode, I can create these veth pairs in 4 seconds

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



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