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ksi_alloc_max(5)

Tunable Kernel Parameters
HP-UX 11i Version 3: February 2007
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NAME

ksi_alloc_max — system-wide limit of queued signals that can be allocated

VALUES

Default

NPROC * 8

Allowed Values

32 through maxint (0x7fffffff)

Recommended

NPROC * 8

DESCRIPTION

ksi_alloc_max is the system-wide limit on the number of queued signals that can be allocated and in use. ksi stands for "kernel signal information" and identifies entries with information about queued signals. There is one per queued signal. Queued signals are used by the sigqueue system call, timer expiration, POSIX real time message queues, and asynchronous I/O. User generated signals (via kill and raise) are not queued.

Who Is Expected to Change This Tunable?

Anyone.

Restrictions on Changing

None. This tunable is dynamic.

When Should the Value of This Tunable Be Raised?

Frequent or heavy use of facilities which use queued signals, may require raising this value. Since the default value is based on the number of processes but the usage is thread based, a large number of threads per process which use queued signals would require a raising the tunable value. When EAGAIN is returned by applications using queued signals, this tunable should be raised.

What Are the Side Effects of Raising the Value?

Increased memory usage, but only if used. Every allocated entry is 96 bytes.

When Should the Value of This Tunable Be Lowered?

Only to control the applications' usage of queued signals.

What Are the Side Effects of Lowering the Value?

If too low, applications using queued signals may fail.

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

ksi_send_max to limit the number of queued signals per process. Since ksi_alloc_max is per system based and ksi_send_max is per process based, the ksi_alloc_max tunable should always be greater.

Note that the default value for ksi_send_max is 32, and for ksi_alloc_max is 'nproc * 8'.

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 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

ksi_alloc_max was developed by HP.

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