vps_chatr_ceiling.5 (2010 09)

vps_chatr_ceiling(5) vps_chatr_ceiling(5)

(Tunable Kernel Parameters)

Modern architectures support very large page sizes (up to 4 GB for IA and up to 1 GB for PA-RISC). Set-

ting vps_chatr_ceiling to very high values (anything above 64 KB) should be done with extreme caution.

It can lead to excessive memory consumption and quickly deplete the amount of free memory available on

the system.

When Should the Value of This Tunable Be Lowered?

This tunable should be lowered if no user application actually needs large pages sized at the current tun-

able value, to minimize the chance of a mistaken or malicious user causing wasted physical frames by

requesting unnecessarily large page sizes.

What Are the Side Effects of Lowering the Value?

One side effect is that applications run with smaller page sizes. Also, the system uses smaller page sizes

for certain system pages.

What Other Tunables 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 parame-

ter 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://www.hp.com/go/hpux-core-docs

AUTHOR

vps_chatr_ceiling

was developed by HP.