netdev - Re: [Patch net-next v2] pktgen: support net namespace

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Date:	Tue, 29 Jan 2013 11:54:37 +0800
From:	Cong Wang <amwang@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [Patch net-next v2] pktgen: support net namespace

On Mon, 2013-01-28 at 19:33 -0800, Eric W. Biederman wrote:
> Cong Wang <amwang@...hat.com> writes:
> 
> > On Mon, 2013-01-28 at 18:36 -0800, Eric W. Biederman wrote:
> >> Cong Wang <amwang@...hat.com> writes:
> >> 
> >> > From: Cong Wang <amwang@...hat.com>
> >> >
> >> > v2: remove a useless check
> >> >
> >> > This patch add net namespace to pktgen, so that
> >> > we can use pktgen in different namespaces.
> >> >
> >> > Cc: Eric W. Biederman <ebiederm@...ssion.com>
> >> > Cc: David S. Miller <davem@...emloft.net>
> >> > Signed-off-by: Cong Wang <amwang@...hat.com>
> >> >
> >> > ---
> >> >  net/core/pktgen.c |  123 +++++++++++++++++++++++++++++++++++------------------
> >> >  1 files changed, 81 insertions(+), 42 deletions(-)
> >> 
> >> Skiming through this again I have spotted what looks like a pretty
> >> major bug.  You are limiting yourself to one network device per network
> >> namespace when the actual limit is one network device per thread.
> >> 
> >> I think you can just kill the dev member of pktgen_net and the two or
> >> three lines of code that touch it.
> >
> > Good point!
> >
> > It is used by pktgen_device_event() to check if the device generates the
> > event is the one in our namespace.
> 
> Which of course is trivial with dev_net()...;
> 
> > It is safe to continue the search even if it is not in our namespace,
> > but it is not efficient. Probably we need to make pktgen_threads list
> > per-namespace.
> 
> Having looked at the code a bit more I think the solution really is to
> make the proc files per network namespace as you are doing, but to leave
> the threads per cpu.  Then it is just a matter of adding for_each_net
> loops in the in the paths that add and remove the proc files.

Hmm?

pktgen creates each thread/proc file for each cpu, since proc files are
per-namespace, we will have nr_cpu*nr_ns such proc files and threads.

It hard to improve this due to this kind of design.

I already finished v3 patch which makes pktgen_threads list per-ns, so
far it works well. I am still testing it.


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