lotsfree_pct.5 (2010 09)

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lotsfree_pct(5) lotsfree_pct(5)

(Tunable Kernel Parameters)

running programs, increasing the probability of having the desired amount of memory on hand without

waiting for freemem to drop below lotsfree

or desfree during the execution of this critical process.

Unless the current

lotsfree is set very low, raising

lotsfree_pct for a process that is not short

lived is fairly pointless as

freemem will almost certainly drop below

lotsfree and more likely even

below

desfree, thus waking up the swapper and allowing for the physical memory to be freed up over

the longer running time as the process requires it.

What are the Side Effects of Raising the Value?

The swap daemon will begin to steal less-frequently accessed pages from running processes. If large

amounts of physical memory is already available without the above situation, this will only slow the

already running processes if they need to swap back in their stolen pages. Large amounts of free physical

memory without short-lived processes that need it (as mentioned above) is simply a waste.

When Should the Value of This Tunable Be Lowered?

The

lotsfree_pct tunable should be lowered on systems where swapping is occurring that still have

more physical memory available than is needed on average, and that have no sudden sharp peaks in

memory usage.

What are the Side Effects of Lowering the Value?

System swap will occur at a lower memory level. If

lotsfree_pct is set too low (keeping in mind that

desfree_pct can never be greater than lotsfree_pct), the system might stall due to memory star-

vation upon new allocation even though swap space is available. The stall would not be fatal, as the swap

daemon will run eventually, but will certainly hamper performance.

What Other Tunable Values Should Be Changed at the Same Time?

lotsfree_pct should be considered when modifying desfree_pct since

lotsfree_pctactsasafirmupper desfree_pct. Attempting to set desfree_pct above

lotsfree_pct is meaningless and will result in an [EINVAL] error.

Notes

Starting with HP-UX 11iv2, HP recommends the use of

lotsfree_pct to specify the upper bound for

the paging daemon.

ERROR VALUES

[EBUSY] Memory resource management infrastructure is busy. Please try later.

[EINVAL] Attempting to set desfree_pct above lotsfree_pct.

[EINVAL] An invalid value is entered that is not an integer between 0 and 30, such as an negative

number.

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

lotsfree_pct was developed by HP.