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

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Date:	Thu, 28 Mar 2013 10:04:10 -0500
From:	Serge Hallyn <serge.hallyn@...ntu.com>
To:	Benoit Lourdelet <blourdel@...iper.net>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [RFC][PATCH] iproute: Faster ip link add, set and delete

Quoting Benoit Lourdelet (blourdel@...iper.net):
> Hello,
> 
> My test consists in starting small containers (10MB of RAM ) each. Each
> container has 2x physical VLAN interfaces attached.

Which commands were you using to create/start them?

> lxc.network.type = phys
> lxc.network.flags = up
> lxc.network.link = eth6.3
> lxc.network.name = eth2
> lxc.network.hwaddr = 00:50:56:a8:03:03
> lxc.network.ipv4 = 192.168.1.1/24
> lxc.network.type = phys
> lxc.network.flags = up
> lxc.network.link = eth7.3
> lxc.network.name = eth1
> lxc.network.ipv4 = 2.2.2.2/24
> lxc.network.hwaddr = 00:50:57:b8:00:01
> 
> 
> 
> With initial iproute2 , when I reach around 1600 containers, container
> creation almost stops.It takes at least 20s per container to start.
> With patched iproutes2 , I have started 4000 containers at a rate of 1 per
> second w/o problem. I have 8000 clan interfaces configured on the host (2x
> 4000).
> 
> 
> Regards
> 
> Benoit
> 
> On 28/03/2013 14:36, "Serge Hallyn" <serge.hallyn@...ntu.com> wrote:
> 
> >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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