netdev - Re: [PATCH net-next] mlx4: use dev_kfree_skb() instead of dev_kfree_skb

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Message-ID: <CAL1qit_pkQ7YBzcAPMSWF4zeFS6yFj18P1yJMvj_Z-7SRMxeRg@mail.gmail.com>
Date:	Wed, 19 Sep 2012 14:21:12 -0700
From:	Ying Cai <ycai@...gle.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Yevgeny Petrilin <yevgenyp@...lanox.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Or Gerlitz <ogerlitz@...lanox.com>
Subject: Re: [PATCH net-next] mlx4: use dev_kfree_skb() instead of dev_kfree_skb_any()

Hi Yevgeny,

It seems all the TxQs are sharing the same interrupt for Tx
completions. Will it be better to have separate interrupt per
num_tx_rings_p_up (8) queues? E.g. for a 16 core system, with 16 * 8
Tx queues, to have 16 interrupts for Tx completions of those 128 Tx
queues?

Also I'm looking at mlx4_en_select_queue(), it is using
__skb_tx_hash(). Use something to achieve XPS may bring better
performances.

Thanks.

On Wed, Sep 19, 2012 at 5:12 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> On Wed, 2012-09-19 at 07:58 +0000, Yevgeny Petrilin wrote:
> > >
> > > Since commit e22979d96a5 (mlx4_en: Moving to Interrupts for TX
> > > completions), we no longer can free TX skb from hard IRQ, but only
> > > from
> > > normal softirq or process context.
> > >
> > > Therefore, we can directly call dev_kfree_skb() from
> > > mlx4_en_free_tx_desc() like other conventional NAPI drivers.
> > >
> >
> > Hi Eric,
> > At the moment the TX completion processing is done from IRQ context.
> > So I think we need to change the driver to work with NAPI for TX
> > completions
> > before making this change.
> >
> > I'll send the patch in a few days.
>
> Oops you're right, it seems I misread e22979d96 commit.
>
> irq term is a bit generic, you might add soft/hard qualifiers to
> distinguish the variant.
>
> Thanks
>
>
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