netdev - Re: Receive steering and hash and cache misses

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Date:	Fri, 2 Apr 2010 10:59:43 -0700
From:	Tom Herbert <therbert@...gle.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Subject: Re: Receive steering and hash and cache misses

On Fri, Apr 2, 2010 at 10:26 AM, Stephen Hemminger
<shemminger@...tta.com> wrote:
>
> Although Receive Packet Steering can use a hardware generated receive hash
> the device driver still causes an unnecessary cache miss on the interrupt
> processing CPU.  The current Ethernet network device driver receive processing
> has the device driver calling eth_type_trans() which causes a the
> interrupt CPU to read the received frame header.
>

It should be possible to deduce the values set by eth_type_trans from
the RX descriptor along with the RX hash.  I'll post the patch getting
rxhash from bnx2x which does this.

> Is there some way the hardware receive hash value could be used to
> steer to the receive CPU, then have the receive CPU find the Ethernet
> type field (eth_type_trans)?
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