Memory statistics

The memory statistics contain the memory-specific information and metrics.

The following sections in the nmon recording file are used to identify the memory statistics:

MEM

Provides statistics on the global memory utilization. This statistic is recorded by default. This section contains the following fields:

Real free %: Percentage of available physical RAM as against the total available RAM.

Virtual free %: Percentage of available paging space as against the total paging space that is allocated.

Real free (MB): Available RAM space in MB.

Virtual free (MB): Available paging space in MB.

Real total (MB): Total physical RAM in MB.

Virtual total (MB): Total paging space size in MB.

Physical (MB): Physical memory, in MB, that is allocated to the shared memory partitions from the shared memory pool at a specific time.
Note: This field is displayed only for an Active Memory Sharing (AMS) partition.

Size of the compressed pool (MB): Size of the compressed pool.
Note: This field is displayed only for the Active Memory Expansion (AME)-enabled partition.

Size of true memory (MB): Size of physical memory in MBs without applying the expansion factor.
Note: This field is displayed only in the Active Memory Expansion (AME)-enabled partition.

Expanded memory size (MB): Logical memory size with expansion factor that is applied on the physical memory. The value of this field is the product of physical memory and expansion factor.
Note: This field is displayed only in the Active Memory Expansion (AME)-enabled partition.

Size of the uncompressed pool (MB): Size of the uncompressed memory pool in MB.
Note: This field is displayed only in the Active Memory Expansion (AME)-enabled partition.

MEMAMS

Provides AMS-specific statistics.

Pool id: Shared memory pool ID.

Weight: Memory weight that is assigned to each LPAR. This field helps hypervisor to assign memory to each LPAR when the physical memory is over-commited. Memory weight is the amount of memory assigned to a LPAR.

Hypervisor Page-in/s: Number of hypervisor page-in operations per second. A hypervisor page-in operation occurs if a page is referenced and is not available in the real memory because the page is paged-out by the hypervisor previously.

HypervisorTime: Time spent in hypervisor paging operations in seconds.

I/O Memory Entitlement(MB): Minimum amount of physical memory that must remain available when the partition requires it for the I/O operations irrespective of physical memory requirements by the partitions.

I/O Memory Use(MB): Used I/O memory entitlement in MB.

I/O Memory HighWater(MB): Highest usage of I/O memory entitlement in MB.

Physical Memory(MB): Physical memory that is available for the partition's logical memory in bytes. The physical memory field is the physical memory in MB that is allocated to shared memory partitions from the shared memory pool at a specific time.

Page Size(MB): Page size that is used by the hypervisor to virtualize the partition’s memory.

Page Coalesced(MB): Page size of the calling partitions' logical real memory in MB that is merged because the page contained duplicate data.

Mempool Page Coalesced (MB): If the calling partition is authorized to access pool-wide statistics of the memory pool, this field contains the amount of logical real memory in MB that is merged. Memory is merged because the page contains duplicate data in the calling partitions' memory pool. If duplicate data is not present, this field is set to zero.

Fraction of CPU consumed in Coalescing pages: If the calling partition is authorized to access pool-wide statistics, the Processor Utilization Resource Register (PURR) cycles are used to merge duplicate data. If duplicate data is not present, this field is set to zero.

MEMNEW

Provides new set of memory metrics. These details are recorded by default.

Process %: Percentage of real memory that is used by the process as against the total real memory that is available in the system.

FScache%: Percentage of real memory that is used by the file system cache as against the real memory.

System%: Percentage of memory that is used by system segments as against the real memory.
Note: System segment is part of the memory segment that is accessed by the AIX kernel and kernel extensions. System segment can not be accessed by AIX processes (applications).

Free%: Percentage of RAM available as against total RAM.

Pinned%

Percentage of pinned memory as against the available memory. This pinned memory is the sum of the following memory segments:

Pinned working segments.
Pinned persistent segments.
Pinned client segments.

User%: Non-system pages are categorized as user segments. user% is the percentage of user segments as against the real memory.
Note: Non-system pages are categorized as user segments.

Compressed pool%: Percentage of real memory that is used by compressed pages as against the total expanded memory available in the system.

MEMUSE

Provides memory usage metrics. This statistics is recorded by default. This section contains the following fields:

%numperm: Percentage of frames of non-computatable pages as against the real memory size.

%minperm: Specifies the time until which the page-stealer steals file or computational pages regardless of repaging rates. The page-stealer targets minimum amount of memory to cache non-computational pages.

%maxperm: Specifies the time after which the page-stealing algorithm steals only file pages.

minfree: Specifies the minimum number of frames on the free list after which the Virtual Memory Manager (VMM) starts to steal pages to refill the free list.

maxfree: Specifies the number of frames on the free list after which page-stealing stops.

%numclient: Percentage of number of client frames as against the total real memory available.

%maxclient: Percentage of maximum amount of memory that must be used to cache non-computational client pages.
Note: The maxclient tunable parameter specifies a limit on the maximum amount of memory that must be used to cache non-computational client pages.

lruable pages: Number of pages available for processing by the Least Recently Used (LRU) algorithm.

PAGE

Provides paging specific metrics. This statistics is recorded by default.

faults: Number of page faults per second.

pgin: Number of page-in operations per second.

pgout: Number of page-out operations per second.

pgsin: Number of page-in operations from paging spaces per second. These values are related to the pages that are paged out.

pgsout: Number of page out operations from paging space per second.

reclaims: Number of page steals per second.

scans: Number of page scans per second.

cycles: Number of clock cycles that are used by page replacement algorithm per second.

compressed pool pgins: Number of page-in operations to the compressed pool per second. This metric is recorded only if active memory expansion (AME) is enabled.

compressed pool pgouts: Number of page-out operations from compressed pool per second.
Note: This metric is recorded only if AME is enabled.

PAGING PagingSpace MB Free, <Paging SpaceName>

Provides statistics about the amount of free paging space in MB. You can use the -P option to enable the recording of this section in the nmon recording file.

LARGEPAGE, LARGEPAGE,Large Page Use

Provides statistics about the large page utilization. Large pages, which have 16 MB size, are used in high-performance environments. The -L option enables these statistics collections in the nmon recording.

Freepages: Number of large pages on the large page free list.

Usedpages: Number of large pages that are in use on the system.

Pages: Total number of large pages on the system.
Note: Total number of pages is the sum of FreePages and Used Pages.

HighWater: Large page high water mark. High water mark is the maximum number of pages that a process had in memory at a point of time.

SizeMB: Size of the large memory page in MB.