*BSD News Article 68101


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From: luigi@labinfo.iet.unipi.it (Luigi Rizzo)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: FreeBSD as a router
Date: 9 May 1996 19:09:04 GMT
Organization: Dip. di Ingegneria dell'Informazione, Univ. di Pisa
Lines: 23
Distribution: world
Message-ID: <4mtfsg$14l8@serra.unipi.it>
References: <4lfm8j$kn3@nuscc.nus.sg> <317CAABE.7DE14518@FreeBSD.org> <4lt098$erq@itchy.serv.net> <Pine.SUN.3.90.960427140735.3161C-100000@tulip.cs.odu.edu> <4mj7f2$mno@news.clinet.fi> <318E6BB1.6A71C39B@lambert.org>
NNTP-Posting-Host: labinfo.iet.unipi.it

In article <318E6BB1.6A71C39B@lambert.org>, Terry Lambert <terry@lambert.org> writes:
|> cards in the machine, and don't buy shared interrupt boards from
|> the Intel OEM products division, buy the discrete interrupt ones
|> from their server products division).

I think that shared interrupts are not that terrible.

For every interrupt (which has a relatively high OS overhead anyways)
you just have to check every board in the chain to see which one
generated the interrupt.  Since this should cost roughly a procedure
call/return for each board, and I doubt that you have to walk more
than 3-4 boards anyways, my feeling is that shared interrupts are
costing you about one microsecond (or less) per interrupt WRT
non-shared interrupts. Anything wrong with this reasoning ?

	Luigi
-- 
====================================================================
Luigi Rizzo                     Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it       Universita' di Pisa
tel: +39-50-568533              via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522              http://www.iet.unipi.it/~luigi/
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