netdev - Re: [bpf-next V2 PATCH 3/8] ixgbe: implement flush flag for ndo_xdp

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Message-ID: <20180604155324.45e10eb7@redhat.com>
Date:   Mon, 4 Jun 2018 15:53:24 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     netdev@...r.kernel.org, Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        liu.song.a23@...il.com, songliubraving@...com,
        John Fastabend <john.fastabend@...il.com>, brouer@...hat.com
Subject: Re: [bpf-next V2 PATCH 3/8] ixgbe: implement flush flag for
 ndo_xdp_xmit

On Mon, 4 Jun 2018 15:19:05 +0200
Daniel Borkmann <daniel@...earbox.net> wrote:

> > +static void ixgbe_xdp_ring_update_tail(struct ixgbe_ring *ring)
> > +{
> > +	/* Force memory writes to complete before letting h/w know there
> > +	 * are new descriptors to fetch.
> > +	 */
> > +	wmb();
> > +	writel(ring->next_to_use, ring->tail);
> > +}  
> 
> Did you double check that this doesn't become a function call? Should this
> get an __always_inline attribute?

I did check this doesn't become a function call.  The same kind of code
happens other places in the driver, but I choose not to generalize
this, exactly to avoid this becoming a function call ;-)

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer