netdev - Re: [PATCH] ixgbe: Introduce new 10GbE driver for Intel 82598 based PCI Express adapters...

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Message-ID: <20070710005725.GA3639@localhost.localdomain>
Date:	Mon, 9 Jul 2007 20:57:25 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	"Veeraiyan, Ayyappan" <ayyappan.veeraiyan@...el.com>
Cc:	Jeff Garzik <jeff@...zik.org>, netdev@...r.kernel.org,
	"Kok, Auke-jan H" <auke-jan.h.kok@...el.com>,
	arjan@...ux.intel.com, akpm@...ux-foundation.org
Subject: Re: [PATCH] ixgbe: Introduce new 10GbE driver for Intel 82598 based PCI	Express adapters...

On Mon, Jul 09, 2007 at 07:21:24AM -0700, Veeraiyan, Ayyappan wrote:
> >From: Neil Horman [mailto:nhorman@...driver.com]
> >Replying to myself...
> >	I've looked through the driver pretty throughly with regards to
> my
> >above
> >concern, and it appears the driver is reasonably free of netpoll issues
> at
> >the
> >moment, at least as far as what we found in e1000 was concerned.  I do
> 
> Thanks for reviewing the code..
> 
> >however,
> >see a concern in the use of the in_netpoll flag within the driver.
> Given
> >that
> >the primary registered net_device, and all the dummy net_devices in the
> >rx_ring
> >point to the same ixgbe_adapter structure, there can be some level of
> >confusion
> >over weather a given rx queue is in netpoll_mode or not.
> 
> The revised driver I am going to post today will not have fake
> netdevs...
> 
> >adapter prforms a netpoll, all the individual rx queues will follow the
> >in_netpoll path in the receive path (assuming misx interrupts are
> used).
> >The
> >result I think is the potential for a large amount of packet reordering
> >during a
> >netpoll operation.  Perhaps not a serious problem, but likely worth
> looking
> 
> Multiple Rx queues are used in non-NAPI mode only, and all Rx queues use
> one netdev (which is associated with the adapter struct). Also, the RSS
> (receive side scaling or rx packet steering) feature is used in multiple
> rx queues mode. In this mode, HW will always select the same Rx queue
> (for a flow) and this should prevent any packet reordering issue.
> 
> 
> >Neil
> 
> Ayyappan

Thank you, I think that satisfies all my concerns.

Regards
Neil
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