swapmem_on(5)

DESCRIPTION

The swapmem_on tunable is obsolete. Processes will always be allowed to use pseudo-swap space if it is available.

In previous versions of HP-UX, system configuration required sufficient physical swap space for the maximum possible number of processes on the system. This is because HP-UX reserves swap space for a process when it is created, to ensure that a running process never needs to be killed due to insufficient swap.

This was difficult, however, for systems needing gigabytes of swap space with gigabytes of physical memory, and those with workloads where the entire load would always be in core. This tunable was created to allow system swap space to be less than core memory. To accomplish this, a portion of physical memory is set aside as "pseudo-swap" space. While actual swap space is still available, processes still reserve all the swap they will need at fork or execute time from the physical device or file system swap. Once this swap is completely used, new processes do not reserve swap, and each page which would have been swapped to the physical device or file system is instead locked in memory and counted as part of the pseudo-swap space.

WARNINGS

Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parameter values. After installation, some tunable parameters may no longer be at the default or recommended values. For information about the effects of installation on tunable values, consult the documentation for the kernel software being installed. For information about optional kernel software that was factory installed on your system, see HP-UX Release Notes at http://docs.hp.com.

AUTHOR

swapmem_on was developed by HP.