Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!sdd.hp.com!hplabs!hplabsz!renglish
From: renglish@hplabsz.HPL.HP.COM (Bob English)
Newsgroups: comp.arch
Subject: Re: HPE Spectrum
Message-ID: <6087@hplabsz.HPL.HP.COM>
Date: 17 Oct 90 22:53:38 GMT
References: <123093@linus.mitre.org> <6058@hplabsz.HPL.HP.COM> <6067@hplabsz.HPL.HP.COM>
Reply-To: renglish@hplabsz.UUCP (Bob English)
Organization: Hewlett-Packard Laboratories
Lines: 28

In article <6067@hplabsz.HPL.HP.COM> renglish@hplabsz.UUCP (Bob English) writes:
>>The Mach port done at the University of Utah, for example, ran
>>about 20% slower than hp-ux because of Mach's penchant for VM aliasing.

>Just a clarification here:  Mach is not inherently 20% slower on
>PA-RISC, but some changes are necessary to eliminate the 20% performance
>penalty.  I chose the example merely to illustrate the difference that
>supporting the PA-RISC architecture properly could mean to performance.
>The changes needed to the machine-independent portion of the Mach VM
>system are minor tweaks, but they make a big difference in performance.

One more clarification:

I have been asked to make it clear that the performance numbers I quoted
came from the Tut project at HP Labs, not the Mach port at the
University of Utah, though the groups had been sharing information on
the two projects.  I did not mean to imply that the Utah Mach port was
slow, nor did I mean to imply that Mach itself was slow.  I merely meant
to answer the original question about what kinds of changes were
necessary to the VM system, and give some insight into the effects those
changes have on system performance.

>"A foot in the mouth is worth...wait a minute...!?!?"

Talk about an understatement :-).

--bob--
renglish@hplabs.hp.com