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

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Message-ID: <20130328042808.GA11672@sergelap>
Date:	Wed, 27 Mar 2013 23:28:08 -0500
From:	Serge Hallyn <serge.hallyn@...ntu.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Stephen Hemminger <stephen@...workplumber.org>,
	Benoit Lourdelet <blourdel@...iper.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [RFC][PATCH] iproute: Faster ip link add, set and delete

Quoting Eric W. Biederman (ebiederm@...ssion.com):
> Serge Hallyn <serge.hallyn@...ntu.com> writes:
> 
> > Quoting Eric W. Biederman (ebiederm@...ssion.com):
> >> Stephen Hemminger <stephen@...workplumber.org> writes:
> >> 
> >> > If you need to do lots of operations the --batch mode will be significantly faster.
> >> > One command start and one link map.
> >> 
> >> The problem in this case as I understand it is lots of independent
> >> operations. Now maybe lxc should not shell out to ip and perform the
> >> work itself.
> >
> > fwiw lxc uses netlink to create new veths, and picks random names with
> > mktemp() ahead of time.
> 
> I am puzzled where does the slownes in iproute2 come into play?

Benoit originally reported slowness when starting >1500 containers.  I
asked him to run a few manual tests to figure out what was taking the
time.  Manually creating a large # of veths was an obvious test, and
one which showed poorly scaling performance.

May well be there are other things slowing down lxc of course.

-serge
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