HP-UX HB v13.00 Ch-22 - Performance and Tuning

HP-UX Handbook – Rev 13.00 Page 10 (of 19)
Chapter 22 Performance & Tuning
October 29, 2013
If there is an insufficient amount of available memory to fork you will receive an error :
cannot fork, not enough virtual memory.
If this error is received , you will need to allocate more device swap. This should be configured
on a disk with no other swap partitions, and ideally of the same size and priority of existing swap
logical volumes to enable interleaving.
In HP-UX , the only reason a process will die for lack of swap space is because of data area
growth (using sbrk),stack growth, or if lazy swap is used.
If pseudo-swap is disabled by setting swapmem_on to 0, there will typically be a need to increase
the amount of device swap in the system to accommodate paging and reserve area. Ideally, in a
modern system paging to disk should be avoided. If there is significant paging to disk and the
buffer cache/file cache has been adjusted to avoid contention , adding RAM would be advisable
for maximum performance.
To monitor memory over time , the vmstat utility is very useful. It can be used to track memory
use over time. The count and iteration fields are similar to sar . By focusing on the avm and free
fields , you can determine if the amount of active open process memory use , and the memory on
the free list are a concern over time. Paging activity can also be assessed.
Example : vmstat –n 60 20 - produces a sample once a minute for 20 minutes.
VM
memory page faults
avm free re at pi po fr de sr in sy cs
4863083 3869884 1388 9 0 0 0 0 0 7867 91843 4134
It will also provide CPU use at the interval:
Cpu procs
us sy id r b w
12 7 82 2 1 0
24 5 71
16 6 78
12 6 81
34 5 60
18 8 74
19 7 74
23 6 70