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3.3.1 svmon

The svmon command provides information about the virtual memory usage by the kernel and

user processes in the system at any given time. For example, to see system-wide information

about the segments (256MB chunk of virtual memory), type the following command as root:

svmon -S

The command prints out segment information sorted according to values in the Inuse field, which

shows the number of virtual pages in the segment that are mapped into the process address space.

Segments of type work with a blank description field belong to user processes. If the LPage is

set to Y, the segment contains large pages. These segments always have 65536 in the Inuse,

Pin, and Virtual fields because this is the number of 4KB pages in the 256MB segment. In other

words, large pages are mapped into the process address space with a granularity of 256MB even

if a process is using a small fraction of it. A segment can have either large pages or small pages,

but not both.

Vsid Esid Type Description LPage Inuse Pin Pgsp Virtual

101810 - work Y 65536 65536 0 65536

161836 - work Y 65536 65536 0 65536

1e09de - work kernel heap - 30392 92 0 30392

9e0 - work kernel heap - 26628 20173 0 26628

190899 - work mbuf pool - 15793 15793 0 15793

20002 - work page table area - 7858 168 7690 7858

0 - work kernel segment - 6394 3327 953 6394

70b07 - work other kernel segments Y 4096 4096 0 4096

c0b0c - work other kernel segments Y 4096 4096 0 4096

1b00bb - work vmm software hat - 4096 4096 0 4096

a09aa - work loader segment - 3074 0 0 3074

Memory overhead associated with HPS communication buffers allocated in support of MPI

processes and IP is shown in the map as other kernel segments. Unlike user segments

with large pages, these segments have just one large page or 4096 4KB pages. The segment

named mbuf pool indicates a system-wide pool of pinned memory allocated for mbufs mostly

used in support of IP. The Pin field shows the number of pinned 4KB pages in a segment (for

example, pages that cannot be paged out). Large pages are always pinned.

To see a segment allocation map organized by process, type the following command as root:

svmon -P

The output is sorted according to the aggregate Inuse value for each process. This is useful in

finding virtual memory demands for all processes on the node. The virtual segment ID (Vsid) is a

unique segment ID that is listed in more than one process when processes share data (for

example, if multiple MPI tasks use shared memory or program text).

Pid Command Inuse Pin Pgsp Virtual 64-bit Mthrd LPage

381118 sppm 448221 3687 2675 449797 Y Y N

IBM pSeries User Manual Page 11