Locality Group Parameters

This section provides generic memory tunables, which apply to any SPARC or x86 system that uses a Non-Uniform Memory Architecture (NUMA).

lpg_alloc_prefer

Description

Controls a heuristic for allocation of large memory pages when the requested page size is not immediately available in the local memory group, but could be satisfied from a remote memory group.

By default, the Oracle Solaris OS allocates a remote large page if local free memory is fragmented, but remote free memory is not. Setting this parameter to 1 indicates that additional effort should be spent attempting to allocate larger memory pages locally, potentially moving smaller pages around to coalesce larger pages in the local memory group.

Data Type

Boolean

Default

0 (Prefer remote allocation if local free memory is fragmented and remote free memory is not)

Range

0 (Prefer remote allocation if local free memory is fragmented and remote free memory is not)

1 (Prefer local allocation whenever possible, even if local free memory is fragmented and remote free memory is not)

Dynamic?

No

Validation

None

When to Change

This parameter might be set to 1 if long-running programs on the system tend to allocate memory that is accessed by a single program, or if memory that is accessed by a group of programs is known to be running in the same locality group (lgroup). In these circumstances, the extra cost of page coalesce operations can be amortized over the long run of the programs.

This parameter might be left at the default value (0) if multiple programs tend to share memory across different locality groups, or if pages tend to be used for short periods of time. In these circumstances, quick allocation of the requested size tends to be more important than allocation in a particular location.

TLB miss activity might be observed by using the trapstat -T command.

Commitment Level

Uncommitted

lgrp_mem_pset_aware

Description

If a process is running within a user processor set, this variable determines whether randomly placed memory for the process is selected from among all the lgroups in the system or only from those lgroups that are spanned by the processors in the processor set.

For more information about creating processor sets, see psrset(1M).

Data Type

Boolean

Default

0, the Oracle Solaris OS selects memory from all the lgroups in the system

Range

• 0, the Oracle Solaris OS selects memory from all the lgroups in the system (default)

• 1, try selecting memory only from those lgroups that are spanned by the processors in the processor set. If the first attempt fails, memory can be allocated in any lgroup.

Dynamic?

No

Validation

None

When to Change

Setting this value to a value of one (1) might lead to more reproducible performance when processor sets are used to isolate applications from one another.

Commitment Level

Uncommitted