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Date: Thu, 21 Nov 2002 11:10:10 -0700
From: "Jeff V. Merkey" <jmerkey@vger.timpanogas.org>
To: Robert Olsson <Robert.Olsson@data.slu.se>
Cc: Jeff Garzik <jgarzik@pobox.com>, linux-kernel@vger.kernel.org
Subject: Re: e1000 fixes (NAPI)
Message-ID: <20021121111010.A31363@vger.timpanogas.org>
References: <15835.56316.564937.169193@robur.slu.se> <20021120164319.A26918@vger.timpanogas.org> <15836.47295.808423.41648@robur.slu.se>
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In-Reply-To: <15836.47295.808423.41648@robur.slu.se>; from Robert.Olsson@data.slu.se on Thu, Nov 21, 2002 at 11:43:11AM +0100
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One other comment.  Does NAPI handle the issue of refilling the RX ring 
from interrupt?  This is the source of the problem, not packet delvery, which
is handled from a softirq handler.  

Jeff

On Thu, Nov 21, 2002 at 11:43:11AM +0100, Robert Olsson wrote:
> 
> Jeff V. Merkey writes:
>  > 
>  > Need another fix.  You need to reinstrument the tasklet schedule in the 
>  > fill_rx_ring instread of doing the whole thing from interrupt.  When the 
>  > system is loaded at 100% saturation on gigbit with 300 byte packets or 
>  > smaller, the driver does not allow any processes to run, and you cannot 
>  > log in via ssh or any user space apps.  This is severely busted.   
>  > 
>  > The later versions of the driver > 4.3.15 all exhibit this behavior and 
>  > are extremely broken.
> 
>  Where have you been? :-)
> 
>  NAPI does RX processing in softirq. RX interrupts are just used to indicate 
>  work. At high loads the consecutive RX polls gets run via ksoftirqd which
>  is under scheduler control also the RX softirq breakes for other work. This 
>  makes the NAPI network stuff as very well behaved kernel citizen and also 
>  gives network performance at any load.
> 
>  More details is in the usenix paper;
>  http://www.cyberus.ca/~hadi/usenix-paper.tgz
> 
>  Cheers.
> 						--ro
> 
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