numa_policy(5) File Formats Manual numa_policy(5)
NAME
numa_policy - physical memory allocation policy on cellular HP-UX servers
VALUES
Default
Allowed values
Integer values or
DESCRIPTION
HP-UX treats large servers as if they are built from componment blocks. Each component block is referred to as a locality and can contain
memory, CPUs and peripherals. HP-UX constructs these component blocks in such a way as to optimize resource alignment.
If a machine has only one locality, it is considered to be an UMA (Unform Memory Architecture) machine. UMA is also a synonym for Symmet-
ric Multiprocessor (SMP).
Large servers use Non-Uniform Memory Access (NUMA) protocols. An application thread can experience variable memory latency depending on
whether it is accessing memory from the same locality upon which it is executing or from a different locality.
HP-UX implements a number of memory allocation features to optimize performance. Users can divide the memory on the system into two
classes of memory: Interleaved and Cell-local.
Interleaved memory delivers uniform latency. It makes multiple localities look like a single bank of uniform memory, delivering the same
average latency for all applications across all CPUs. This is very useful in spreading the memory load across all the localities.
Cell-local memory delivers low latency (high performance) to a process running in the same cell as the memory it accesses. Conversely,
references from a remote cell will have a much higher latency.
Users can configure cell-local memory using the HP-UX command or
The dynamic kernel tunable allows users to define how interleaved and cell-local memory are utilized. There are five possible values for
this tunable:
This is the default value. HP-UX will autosense the right policy based on the
mode in which HP-UX is operating. See for more details on mode.
This is the default policy in LORA mode.
This policy directs HP-UX to use memory from the locality closest to the allocating CPU for user memory allocations. It will
select the locality by first honoring any locality policies specified in or If no locality policies are specified, then all
memory is allocated from the locality closest to the allocating CPU. See mpsched(1) for more information.
This policy directs HP-UX to override any locality policies supplied via
or and allocate all memory from the interleaved. Cell-local memory is allocated when there is insufficient interleaved mem-
ory.
This policy is like setting
to except that all text and library data segments are allocated from the interleaved domain. This setting is useful for
servers running highly threaded applications. This setting has a similar effect to the command's +id option (this option is
only available on Integrity systems), but on a system wide basis.
This is the default policy in SMP mode.
In a machine configured with a mix of cell-local memory and interleaved memory, HP-UX makes intelligent decisions on how to
use the memory by distinguishing between private memory and shared memory. For example, Memory allocated to private objects
(stack, heap, private files, and so on) is likely to come from cell-local memory. Memory allocated to shared objects (shared
files, System V shared memory) is allocated from interleaved memory unless the user specifies otherwise using for files or
uses one of the memory options in
Restrictions on Changing
Changes to this tunable take effect on memory allocated subsequent to the change. Any memory created before the change will not be
affected.
When Should the Value of This Tunable Be Changed to 1?
should be set to 1 only if all performance-sensitive applications on the system have a high degree of locality of access. That is, if the
majority of references to shared memory are from processes running on the same cell where the memory has been allocated, then setting will
have a positive effect on performance. Changing the value to 1 should be done after sufficient memory has been designated as cell-local
using and the machine has been rebooted.
When Should the Value of This Tunable Be Changed to 2?
can be set to 2 if the workload has a low degree of locality to a cell and it is not possible to change the source code. Changing the
value to 2 should be done after sufficient memory has been designated as interleaved using and the machine has been rebooted. Setting the
tunable to 2 only makes sense in a mixed environment in which some applications can benefit from cell-local memory, and others cannot.
When Should the Value of This Tunable Be Changed to 3?
can be set to 3 if the all the performance-sensitive applications on the system have a high degree of locality of access and if the work-
load is threaded. Changing the value to 3 should be done after sufficient memory has been designated as cell-local using and the machine
has been rebooted.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its meaning changed in future releases of
HP-UX.
Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parameter values. After installation,
some tunable parameters may no longer be at the default or recommended values. For information about the effects of installation on tun-
able values, consult the documentation for the kernel software being installed. For information about optional kernel software that was
factory installed on your system, see at
AUTHOR
was developed by HP.
SEE ALSO
chatr_ia(1), mpsched(1), parmodify(1M), fadvise(2), shmget(2).
Tunable Kernel Parameters numa_policy(5)
