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

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Message-ID: <20130328133652.GA6652@sergelap>
Date:	Thu, 28 Mar 2013 08:36:52 -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):
> >> 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.
> 
> Apparently iproute is involved somehwere as when he tested with a
> patched iproute (as you asked him to) the lxc startup slowdown was
> gone.
> 
> > May well be there are other things slowing down lxc of course.
> 
> The evidence indicates it was iproute being called somewhere...

Benoit can you tell us exactly what test you were running when you saw
the slowdown was gone?

-serge
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