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Date:	Fri, 24 Aug 2007 11:51:10 -0500
From: (Linas Vepstas)
To:	Stephen Hemminger <>
Cc:	Jan-Bernd Themann <>,
	Thomas Klein <>,,
	Jan-Bernd Themann <>,
	netdev <>,
	linux-kernel <>,
	Christoph Raisch <>,
	linux-ppc <>,,
	Eder <>,
	Stefan Roscher <>
Subject: Re: RFC: issues concerning the next NAPI interface

On Fri, Aug 24, 2007 at 08:52:03AM -0700, Stephen Hemminger wrote:
> You need hardware support for deferred interrupts. Most devices have it (e1000, sky2, tg3)
> and it interacts well with NAPI. It is not a generic thing you want done by the stack,
> you want the hardware to hold off interrupts until X packets or Y usecs have expired.

Just to be clear, in the previous email I posted on this thread, I
described a worst-case network ping-pong test case (send a packet, wait
for reply), and found out that a deffered interrupt scheme just damaged
the performance of the test case.  Since the folks who came up with the
test case were adamant, I turned off the defferred interrupts.  
While defferred interrupts are an "obvious" solution, I decided that 
they weren't a good solution. (And I have no other solution to offer).


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