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Date:      Thu, 13 Jul 2000 11:34:14 -0400 (EDT)
From:      "Brandon D. Valentine" <bandix@looksharp.net>
To:        Stephen McKay <mckay@thehub.com.au>
Cc:        Stefan Esser <se@FreeBSD.ORG>, Bill Paul <wpaul@FreeBSD.ORG>, freebsd-current@FreeBSD.ORG
Subject:   Re: dc driver and underruns (was: Strangeness with 4.0-S)
Message-ID:  <Pine.BSF.4.21.0007131131141.26547-100000@turtle.looksharp.net>
In-Reply-To: <200007131246.WAA05918@dungeon.home>

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On Thu, 13 Jul 2000, Stephen McKay wrote:

>>Guess it will show up if you measure latencies (or your application is
>>doing lots of RPCs). But as soon as there is a cheap 100baseT switch in
>>the path to the destination, there will be store-and-forward at work ;-)
>
>Does anyone here actually measure these latencies?  I know for a fact
>that nothing I've ever done would or could be affected by extra latencies
>that are as small as the ones we are discussing.  Does anybody at all
>depend on the start-transmitting-before-DMA-completed feature we are
>discussing?

I don't like the idea of removing that feature.  Perhaps it should be a
sysctl or ifconfig option, but it should definitely remain available.
Those minute latencies are critical to those of us who use MPI for
complex parallel calculations.

Brandon D. Valentine
-- 
bandix at looksharp.net  |  bandix at structbio.vanderbilt.edu
"Truth suffers from too much analysis." -- Ancient Fremen Saying



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