From mboxrd@z Thu Jan  1 00:00:00 1970
From: Hannes Frederic Sowa <hannes@stressinduktion.org>
Subject: Re: [PATCH net-next] mlx4: optimize xmit path
Date: Sun, 28 Sep 2014 01:44:27 +0200
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Cc: Alexei Starovoitov <ast@plumgrid.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Eric Dumazet <edumazet@google.com>,
	John Fastabend <john.r.fastabend@intel.com>,
	Linux Netdev List <netdev@vger.kernel.org>,
	Amir Vadai <amirv@mellanox.com>,
	Or Gerlitz <or.gerlitz@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>,
	Or Gerlitz <gerlitz.or@gmail.com>
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Hi Eric,

On Sun, Sep 28, 2014, at 00:56, Eric Dumazet wrote:
> -       ring->cons += txbbs_skipped;
> +
> +       /* we want to dirty this cache line once */
> +       ACCESS_ONCE(ring->last_nr_txbb) = last_nr_txbb;
> +       ACCESS_ONCE(ring->cons) = ring_cons + txbbs_skipped;
> +

Impressive work!

I wonder if another macro might be useful for those kind of
dereferences, because ACCESS_ONCE is associated with correctness in my
mind and those usages only try to optimize access patterns.
Does OPTIMIZER_HIDE_VAR generate the same code?

Bye,
Hannes