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From: grog@lemis.de (Greg Lehey)
Organisation: LEMIS, Schellnhausen 2, 36325 Feldatal, Germany
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Reply-To: grog@lemis.de (Greg Lehey)
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Subject: Re: larry: you might want to add this to lmbench (but i'm not sure)
To: rminnich@Sarnoff.COM (Ron G. Minnich)
Date: Sat, 11 Nov 1995 10:02:43 +0100 (MET)
Cc: hackers@freebsd.org (FreeBSD Hackers)
In-Reply-To: <Pine.SOL.3.91.951110110255.13530A-100000@morse> from "Ron G. Minnich" at Nov 10, 95 11:15:34 am
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Ron G. Minnich writes:
> 
> this program does a very simple thing: 
> 1) open a file
> 2) call write with an invalid address, viz: 
> 		write(fd, x, 5);
> 	where x is (void *) 0x40000000
> 
> it does this as many times as you ask. What it's measuring is correlated 
> to the raw performance of the system's ability to look up a vm region or 
> segment or object given a virtual address. It is not a pure measure, 
> since systems that do a lot of work before checking the arguments 
> (freebsd) will fare worse than systems that just check the arguments up 
> front for validity (linux). On the other hand, all the system calls that 
> happen a lot have to do this operation, so you probably want this type of 
> thing to be fast. 

Forgive me if I'm not critical :-)  I just tried it out on two
486DX/2-66s, one running BSD/386 1.1 and the other running FreeBSD
951004 SNAP.  I think the numbers (for 100000 iterations) speak for
themselves.

BSD/386:	10.19 real         0.33 user         9.61 sys
FreeBSD:	54.25 real         0.82 user        52.67 sys

People may argue that this is a silly benchmark, but I still think we
should be interested to know why FreeBSD takes over 5 times as long to
run this program.

Greg