Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!udel!haven.umd.edu!umd5!cogsci!wjb
From: wjb@cogsci.cog.jhu.edu
Newsgroups: comp.benchmarks
Subject: Re: Which benchmarks are useless?
Message-ID: <02.May.91.132611.54@cogsci.cog.jhu.edu>
Date: 2 May 91 17:26:11 GMT
References: <2502@spim.mips.COM> <21720006@hpfcso.FC.HP.COM>
Organization: JHU Cognitive Science Center, Baltimore, MD
Lines: 20

In article <21720006@hpfcso.FC.HP.COM> jvm@hpfcso.FC.HP.COM (Jack McClurg)
 writes:
>patrick@convex.COM (Patrick F. McGehearty) /  4:51 pm  Apr 29, 1991 / wrote:
>> [benchmarks and caching of process id for getpid() calls]
>
>[disavows any such caching in HPUX]

	I've heard this "rumor" as well.  I always wondered why people
didn't try to test it out by comparing getpid() and getppid() times.  Your
PID may not ever change, but your PPID will change to 1 if your parent exits.
This would appear to require that getppid() enter the kernel.  Actually, the
real way to speed up both of these system calls is to map a page of memory
read-only into the data space of the process and have the program read this
data directly from where the kernel stores it.  I guess this is another
example of the dangers of micro benchmarks and making assumptions about how
different system functions are implemented.

					Bill Bogstad