The new generation of the Intel® Itanium® 2 processor incorporates several
advanced features and improvements, including multiple cores per
processor and multiple hardware threads per core. The HP-UX 11i
v3 operating system is enhanced to support the new multiple hardware
thread feature called the Hyper-Threading (HT) Technology.
The new generation of the Intel® Itanium® 2 processor supports two-way
hardware multi-threading where the core resources are shared between
two hardware threads (two independent streams of instructions).
Each hardware thread appears as a complete processor to the user
applications and to the operating system.
The HT Technology increases the functional and instructional
throughput by making use of the underutilized core resources and
idling cycles caused by the memory stalls. However, the out-of-box
performance of applications on HT can vary greatly due to various
factors. Therefore, the HT Technology is integrated with the HP-UX's
existing partitioning technology, specifically the processor set,
as a way to offer simultaneous availability of processors with HT
enabled and disabled dynamically at the processor set boundary.
This feature is called the Dynamic LCPU.
The definition of HP-UX processor sets is expanded to include
a new attribute - LCPU attribute. This allows dynamically enable
or disable all LCPUs within a pset. Disabling LCPU renders the processor
cores as a single-threaded processor. In this model, the processor
set provides a “quarantine zone” for applications that
do not perform well with HTs by allowing the applications to run
on processors without hardware threading. Other applications that
perform well with HTs can run in processor sets with LCPUs enabled.
Summary
of Change |
 |
What’s
New for Customers Migrating from HP-UX 11i v1 September 2005?
The following existing system calls have been expanded to
support the Itanium® 2 Hyper-Threading
Feature and Dynamic LCPU:
mpctl(2) -
additional command options to query the physical processor core
topology at either the system or processor set level.
pset_ctl(2) - additional command options
to query the physical processor core topology at the processor set
boundary level.
pstat_getprocessor(2) - new fields to report sibling
logical processors which belongs to the same physical processor
core.
pset_setattr(2) - new command option to
dynamically enable or disable LCPU attribute of a non-default processor
set.
__pset_rtctl(2) - new command option to
dynamically enable or disable LCPU attribute of an RTE processor
set.
A new dynamic attribute is introduced to control the LCPU
attribute of the default processor set:
lcpu_attr(5) -
dynamic kernel tunable value to enable or disable LCPU attribute
of the default processor set.
Impact |
|
The Dynamic LCPU feature impacts customers using the Itanium® 2 with the Hyper-Threading
feature.
Compatibility |
|
There is no impact with binary compatibility.
Performance |
|
Some applications may benefit from Hyper-Threading. Refer
to the “Dynamic Logical Processors for Hyper-Threading on
HP-UX 11i V3” white paper, available on http://docs.hp.com, for further details on application considerations
on HT.
Documentation |
|
The “Dynamic Logical Processors for Hyper-Threading
on HP-UX 11i V3” white paper is available on http://docs.hp.com.
The following manpages are available for further information:
Obsolescence |
|
Not applicable.
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