Tuning memory resources

Tuning memory-bound systems

If the system is found to be memory bound there are a number of things that can be done. The most obvious and that which will probably bring the most benefit is to add more physical memory to your system and retune it. If this is not possible then a number of alternatives exist:

NOTE: If you increase the amount of physical memory in your system to 32MB or more, run the iddeftune(ADM) command to increase the values of certain kernel parameters.

If the system appears to be constantly paging, this may be the result of the values of GPGSLO and GPGSHI being too high. This causes vhand to page out pages while a large number of free pages still exist. Lowering these values could delay the onset of paging but might cause the system to begin swapping out whole processes instead if memory drops to zero. If no compromise can be met then the system needs more memory.

If the number of pages on the free list falls below GPGSLO, vhand begins moving pages out of memory. vhand continues to do this until the number of pages on the free list reaches GPGSHI.

If the difference between GPGSLO and GPGSHI is too great, this may cause an I/O bottleneck while the kernel attempts to write the contents of many dirty pages to disk.

If the values of GPGSLO and GPGSHI are close together, vhand will be active for a shorter period of time but more often. If vhand is constantly active, its usage of the CPU may degrade performance.

Next topic: Reducing disk activity caused by swapping and paging
Previous topic: Identifying memory-bound systems

© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003