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

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Date:	Mon, 28 Jan 2013 19:33:58 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Cong Wang <amwang@...hat.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [Patch net-next v2] pktgen: support net namespace

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.

The per interface proc files would of course only show up in a single
network namespace.

It is still a proc file per network namespace and per cpu but that is
better than threads that try and consume cpu resources.  Especially
since the threads when runnign try and consume 100% of the cpu for
transmitting packets.

Eric
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