swapmem_on(5) [hpux man page]
swapmem_on(5) OBSOLETE swapmem_on(5) NAME
swapmem_on - OBSOLETE kernel tunable parameter DESCRIPTION
The tunable is obsolete.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 tun- able values, consult the documentation for the kernel software being installed. For information about optional kernel software that was factory installed on your system, see at AUTHOR
was developed by HP. Tunable Kernel Parameters swapmem_on(5)
Check Out this Related Man Page
nswapdev(5) File Formats Manual nswapdev(5) NAME
nswapdev - maximum number of devices that can be enabled for swap VALUES
Default Allowed values DESCRIPTION
Swap devices are managed in a table for easier indexing in the kernel. sets the kernel variable responsible for the upper limit on this table, and thus the upper limit to devices which can be used for swap. Who is Expected to Change This Tunable? Anyone. Restrictions on Changing Changes to this tunable take effect at the next reboot. When Should the Value of This Tunable Be Raised? If another swap device is added to the system which would increase the number of devices above and returns to the caller (see the swapon(2) manpage). What Are the Side Effects of Raising the Value? More devices can be added to the system, and the kernel will need a little more memory for the table. A small performance side effect of the kernel having to scan more devices to check for a duplicate device during is also true, but realistically negligible. When Should the Value of This Tunable Be Lowered? Only if you are sure the system will never go over a certain number of swap devices, and you wish to lower this tunable to save a small amount of kernel memory and kernel performance during operations. What Are the Side Effects of Lowering the Value? No side effects other than the primary and presumably desired new limitation on the number of swap devices. What Other Tunable Values Should Be Changed at the Same Time? None. WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its meaning changed in future releases of HP-UX. 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 tun- able values, consult the documentation for the kernel software being installed. For information about optional kernel software that was factory installed on your system, see at AUTHOR
was developed by HP. Tunable Kernel Parameters nswapdev(5)