From: david@ods.com (David Engel) Subject: Re: find 3.7 and fileutils 3.3 uploaded Date: Wed, 29 Jul 1992 21:06:22 GMT
davidsen@ariel.crd.GE.COM (william E Davidsen) writes:
: BTW: how much os a hit does the library take on using the jump table?
: Between the extra level of indirect, dumping the cache and pipeline
: twice as often, and paging on small systems, this looks like a potential
: 5% increase in clock time. Do you have numbers? I see people taking the
The very rough measurements I did a couple of months ago showed a hit of
about 2-4%. The programs I tested were mostly I/O bound and the method
I used to time them was rather crude though, so I don't know how realistic
those numbers are. If someone has any compute bound programs that exercise
libc, I like to know about it so I can try them.
: Note, I'm looking for clarification rather than saying "this is bad."
: My guess of what it adds to small systems calls could be way off, etc.
: I'm well aware of the benefits of jump tables, just concerned about
: possible performance costs. Maybe the only hit is the extra pieline
: dump, I suspect the table would be memory, if not in cache, all the
: time.
Yes, if all or most all progarms use the jump-table libs (like they do on
my system :), the jump-table would almost always be in memory.
David
-- David Engel Optical Data Systems, Inc. david@ods.com 1101 E. Arapaho Road (214) 234-6400 Richardson, TX 75081