NFS Performance Tuning for HP-UX 11.0 and 11i Systems

nfs performance tuning for hp-ux 11.0 and 11i systems page 110

Notes:

Page 110July 22, 2002

buffer

cache

Should you use static or dynamic

allocation in your environment?

DynamicMemory pressure or small memory system

DynamicNone of the above

Static

You have determined the optimal cache size

and have sufficient memory

Static

You use variable memory page sizes and

experience memory fragmentation

Static

You plan on adding more memory to the

system and don’t want buffer cache affected

Under most circumstances, the dynamic allocation method is the recommended

method of allocating system memory to buffer cache. However, there are some

environments where the static allocation method might offer some benefits.

If you have experimented with different amounts of buffer cache on a given client

and have determined the optimal size of the cache (i.e. provides the best

performance for your applications) then the easiest solution is to fix buffer cache at

that size. Also, once you’ve determined the optimal size of the cache the last thing

you want is for this size to inadvertently change without your consent. In the case

where you need to add more physical memory to the system, perhaps due to

growing application requirements, this will affect your total buffer cache size if you

use dynamic allocation since it calculates the cache size as a percentage of

memory.

In rare cases, customers using variable memory page sizes and dynamic buffer

cache have reported problems of memory fragmentation and resulting poor

performance. Static buffer cache avoids this issue by allocating all of its memory

resources at system boot time in contiguous space.