Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!decvax!ucbvax!sdcsvax!darrell
From: darrell@sdcsvax.UUCP
Newsgroups: mod.os
Subject: Re: kernel servers vs. user servers.
Message-ID: <2492@sdcsvax.UCSD.EDU>
Date: Wed, 21-Jan-87 09:56:45 EST
Article-I.D.: sdcsvax.2492
Posted: Wed Jan 21 09:56:45 1987
Date-Received: Wed, 21-Jan-87 21:36:37 EST
Sender: darrell@sdcsvax.UCSD.EDU
Organization: Codex Corp, a division of Motorola; Canton, MA, USA
Lines: 21
Approved: mod-os@sdcsvax.uucp

--

  Some people have commented that it is a sorry state of affairs that things
must reside in the "kernel" to be efficient. Others have made a statement that
"user servers" are the way to go. Well, in the system that I am working on the
only difference between a "kernel" server and a "user" server is that in a 
kernel server no cache or TLB flushing occurs. I can still run the debugger
and test the kernel process, just as I would for a user process. Thus, short
of a hardware performance improvement there is no difference.

  As for why the kernel server runs faster, well it is actually attributed to
two reasons - first, as mentioned no cache or TLB flushing occurs and secondly
the scheduling of "kernel" processes (AKA servers) is realtime, and based on
priority. User processes are scheduled accroding to a timeslicing scheme which
doesn't work well with "server" type things.



                     Chuck Wegrzyn, not a Codex employee.

--