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Date: Mon, 8 Jul 1996 23:19:34 -0700
From: Andrew McRae <amcrae@cisco.com>
Message-Id: <199607090619.XAA06381@doberman.cisco.com>
To: bde@zeta.org.au
Cc: hackers@freebsd.org
Subject: Re: Some interesting papers on BSD ...
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bde@zeta.org.au (Bruce Evans):
> The effect of fixing the spl's was very large even on unloaded systems.
> TCP to localhost speeded up by 25% or so on a 486/33, because it
> involves a surprisingly large number of spl's (40000/MB IIRC, but this
> seems too surprisingly large) and each spl pair used 26 PIC i/o
> instructions under 386BSD-0.0.  The speedup would be a factor of about
> 10-20 on a fast Pentium (from 1 or 2 MB/s to about 20MB/s).  Of course,
> a better implementation using the PIC would only involve 2 or 4 i/o
> instructions per spl pair.

For some quantitative measurements of the effect of spl* on
networking and friends, see ftp://ftp.cisco.com/amcrae/hardprof.PS
(Usenix 93 paper on hardware profiling of 386BSD). The numbers
are instructive, but outdated now. Perhaps I will get around
to profiling the current kernel someday.

Also, ftp://ftp.cisco.com/amcrae/plug_n_play.PS is the AUUG paper
on integrating PC-Card into FreeBSD. Perhaps these papers
could be referenced from the web page somewhere.

Cheers,
Andrew McRae