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Date:      Wed, 04 Mar 1998 18:56:20 -0800
From:      Mike Smith <mike@smith.net.au>
To:        Matthew Thyer <Matthew.Thyer@dsto.defence.gov.au>
Cc:        Mike Smith <mike@smith.net.au>, shimon@simon-shapiro.org, current@FreeBSD.ORG
Subject:   Re: silo overflows (Was Re: 3.0-RELEASE?) 
Message-ID:  <199803050256.SAA23678@dingo.cdrom.com>
In-Reply-To: Your message of "Thu, 05 Mar 1998 12:37:19 %2B1030." <34FE08D7.159A2AD@dsto.defence.gov.au> 

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> 
> Simon is seeing an error message, so am I.  I think many people
> are also seeing it.

No kidding.  I've been seeing it for years.  It wouldn't be in the code 
if it was an impossibility.

> Now the frequency of this message has changed a lot since the 2.1R
> days which would seem to indicate that something can be done
> about the processing of interrupts to reduce the occurrance of
> FIFO overflows.

Quite possibly, yes.  Changes were actually made to *improve* the 
interrupt handling performance of the driver.  Check the CVS logs for 
references to "fast interrupts", and the use of the RI_FAST flag.

But without any testing or hard numbers, your claim above is 
meaningless.  You haven't given any context, or demonstrated with 
similar machines and loads side-by-side that there has been any 
quantifiable change in system behaviour.  Perhaps its your usage 
profile that's changed?

> Also this problem occurs on many machines Pentium 166, Pentium 100
> etc.  It does not only occur on 486SX25's or other such low end
> machines.  (I have a Pentium 166 and a V.FC modem).

All this tells us is that the problem is not related to marginal CPU 
speed, but we knew this already.

> But maybe it should be seriously discussed.

It has been.  We know about it.  But nobody that cares enough about it 
has taken the time to analyse the problem.  I tried to suggest, in my 
response to Simon, how one might go about doing this, in the 
(apparently vain) hope that someone might take me up on it.

Shall we say that slagging the 'sio' driver certainly isn't the best way
to start?
-- 
\\  Sometimes you're ahead,       \\  Mike Smith
\\  sometimes you're behind.      \\  mike@smith.net.au
\\  The race is long, and in the  \\  msmith@freebsd.org
\\  end it's only with yourself.  \\  msmith@cdrom.com



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