re: 2.2.1 SMP Scalability to 4-way

urbanski@us.ibm.com
Sun, 31 Jan 1999 09:36:03 -0700

Well it looks like I should have investigated more, you're right. I
assumed this application operated similarly on both operating systems, but
it does not. On Solaris it spawns a single multi-threaded process which (I
assume) uses the correct number of threads. On Linux, it spawns multiple
instances of a process - but uses the wrong number! If given the parameter
P=2, which is supposed to mean 2 CPU's it spawns 3 processes. So at P=4 it
was spawning 5 processes. Consider this a retraction.

Jay Urbanski
Netfinity Systems Engineer
IBM Advanced Technical Support
MCSE, PSE, Certified Solaris Systems Administrator
(817)962-3597 TL 522-3597
(817)962-7307 fax
(800)413-9093 pager
urbanski@us.ibm.com

Mark Hahn <hahn@coffee.psychology.mcmaster.ca> on 01/31/99 10:30:39 AM

To: Jay Urbanski/Dallas/IBM
cc:
Subject: re: 2.2.1 SMP Scalability to 4-way

unfortunately, your message was fairly unuseful, since it was missing
any information about what the QC app was actually doing. for instance,
was it doing lots of IPC? file IO? was it thrashing? mmaped IO?
if none of the above, do you theorize that it was thrashing pages
due to Linux's lack of page coloring? Linux developers are definitely
interested, but you have to remember that for the apps developers most
frequently see (parallel makes), Linux scales _nearly_perfectly_.

claiming Linux can't scale to 4x is downright irresponsible unless
you define exactly what you mean...

regards, mark hahn.

--
operator may differ from spokesperson.
hahn@coffee.mcmaster.ca
                                              http://java.mcmaster.ca/~hahn










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