netdev - Re: [PATCH 0/2] macvlan: Avoid unnecessary multicast cloning

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Date:	Mon, 30 May 2016 19:27:59 +0300
From:	Lennert Buytenhek <buytenh@...tstofly.org>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 0/2] macvlan: Avoid unnecessary multicast cloning

On Mon, May 30, 2016 at 04:17:52PM +0800, Herbert Xu wrote:

> > Commit 412ca1550cbecb2c ("macvlan: Move broadcasts into a work queue")
> > moved processing of all macvlan multicasts into a work queue.  This
> > causes a noticable performance regression when there is heavy multicast
> > traffic on the underlying interface for multicast groups that the
> > macvlan subinterfaces are not members of, in which case we end up
> > cloning all those packets and then freeing them again from a work queue
> > without really doing any useful work with them in between.
> 
> OK so your motivation is to get rid of the unnecessary memory
> allocation, right?

That and stack switches to kworker threads and serialisation on
the bc_queue queue lock.