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Date: Tue, 17 Sep 2002 14:49:11 -0700 (PDT)
Message-Id: <20020917.144911.43656989.davem@redhat.com>
To: jgarzik@mandrakesoft.com
Cc: akpm@digeo.com, manfred@colorfullife.com, netdev@oss.sgi.com,
       linux-kernel@vger.kernel.org
Subject: Re: Info: NAPI performance at "low" loads
From: "David S. Miller" <davem@redhat.com>
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   From: Jeff Garzik <jgarzik@mandrakesoft.com>
   Date: Tue, 17 Sep 2002 17:54:42 -0400

   David S. Miller wrote:
   > Any driver should be able to get the NAPI overhead to max out at
   > 2 PIOs per packet.
   
   Just to pick nits... my example went from 2 or 3 IOs [depending on the 
   presence/absence of a work loop] to 6 IOs.
   
I mean "2 extra PIOs" not "2 total PIOs".

I think it's doable for just about every driver, even tg3 with it's
weird semaphore scheme takes 2 extra PIOs worst case with NAPI.

The semaphore I have to ACK anyways at hw IRQ time anyways, and since
I keep a software copy of the IRQ masking register, mask and unmask
are each one PIO.