netdev - Re: [PATCH RFC]: napi

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Message-ID: <46AB862C.9040507@garzik.org>
Date:	Sat, 28 Jul 2007 14:08:44 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	David Miller <davem@...emloft.net>
CC:	shemminger@...ux-foundation.org, netdev@...r.kernel.org,
	hadi@...erus.ca, rusty@...tcorp.com.au
Subject: Re: [PATCH RFC]: napi_struct V4

David Miller wrote:
> From: Jeff Garzik <jeff@...zik.org>
> Date: Wed, 25 Jul 2007 22:00:31 -0400
> 
>> David Miller wrote:
>>> From: Jeff Garzik <jgarzik@...ox.com>
>>> Date: Wed, 25 Jul 2007 21:55:08 -0400
>>>
>>>> I don't see any logic to your request, only added overhead for no reason.
>>> There may be some flawed logic in what Stephen stated, but
>>> the change really is needed.
>>>
>>> It must be atomic to execute the:
>>>
>>> 	enable_interrupts();
>>> 	netif_rx_complete();
>>>
>>> sequence wrt. the same code path in the interrupt handler.
>> Sure.  And how did the existing code fail to achieve that?
> 
> The interrupt handler can run on another cpu in betwen those two
> statements, running the NAPI test-and-do-something operations in
> parallel with the netif_rx_complete() which causes problems as Rusty
> and I discussed yesterday.

That's a performance/parallelization regression from current NAPI :(

	Jeff



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