Process and thread “gang scheduling, Hp-ux 11.10 sca enhancements – HP 9000 V2600 SCA User Manual
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Chapter 6
HP-UX Operating System
HP-UX on the V2500/V2600
/usr/sam/lib/kc/tuned
Refer to the SAM online help for examples and details on using kernel
parameters.
Process and Thread “Gang Scheduling”
HP-UX V11.0 includes support for kernel threads and provides a “gang
scheduling” feature for managing how threads belonging to the same
process or application are executed.
The HP-UX gang scheduler permits a set of MPI processes, or multiple
threads from a single process, to be scheduled concurrently as a group.
Gang scheduling is enabled and disabled by setting the
MP_GANG
environment variable to
ON
or
OFF
.
The gang scheduling feature can significantly improve parallel
application performance in loaded timeshare environments that are
oversubscribed. Oversubscription occurs when the total number of
runnable parallel threads, runnable MPI processes, and other runnable
processes exceeds the number of processors in the system.
Gang scheduling also permits low-latency interactions among threads in
shared-memory parallel applications.
Only applications using the HP-UX V11.0 MPI or pthread libraries can
be gang scheduled. Because HP compiler parallelism is primarily built
on the pthread library, programs compiled with HP compilers can benefit
from gang scheduling.
For more details, refer to the gang_sched(7) man page.
HP-UX 11.10 SCA Enhancements
Hewlett-Packard’s Scalable Computing Architecture (SCA) design allows
for multiple resource localities (or “locality domains”) to be combined to
form a single system running a single instance of the HP-UX operating
system. One example of an SCA system is a multiple-cabinet HP V2500/
V2600 server where each cabinet comprises a locality domain.
HP-UX V11.10 provides SCA enhancements. These include a utility
(
mpsched
) as well as system calls and library routine extensions for
controlling how processes and threads are launched, where they are
placed for execution, whether they may migrate (move) during execution,
and how they use memory. These SCA interfaces and programming