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ksi_alloc_max.5 (2010 09)

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ksi_alloc_max(5) ksi_alloc_max(5)
(Tunable Kernel Parameters)
NAME
ksi_alloc_max - system-wide limit of queued signals that can be allocated
VALUES
Default
33600
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 sig-
nals. 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 sys-
tem 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 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
ksi_alloc_max was developed by HP.
SEE ALSO
kctune(1M), kill(2), sigqueue(2), ksi_send_max(5).
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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