NAME
nkthread — limits the number of threads allowed to run simultaneously
VALUES
Default
((nproc*2)+16)
or
8416
Allowed values
200 - 250,000
nkthread
must be greater than
nproc + 100.
nkthread
must be greater than
max_thread_proc.
This may be set higher, but more will not be used.
Recommended values
Unless there are heavily threaded applications on the system,
the default formula is adequate if
nproc
is tuned correctly.
DESCRIPTION
The
nkthread
tunable controls the absolute number of threads allowed on a system at
any given time.
Increasing it will allow more threads, and lowering it will restrict the
number of threads.
It can be determined that
nkthread
is too low when the
kthread: table is full
message is seen in the message buffer.
The message can be read via
dmesg
or
syslog.
This message indicates that an application was unable to create a thread.
Setting
nkthread
too low can cause application failures due to an inability to create
new threads or fork new processes.
It can be determined how many threads have been used simultaneously
prior to the above message by calling
pstat_dynamic
and examining the
psd_numkthreadsallocd.
This field indicates the "high water" mark of the number of threads
that have been simultaneously used.
Who Is Expected to Change This Tunable?
Anyone expecting to run large numbers of threads.
Restrictions on Changing
None. This tunable is dynamic.
When Should the Value of This Tunable Be Raised?
This value should be increased, either directly or as a result of tuning
nproc,
on most systems that are running many threads or processes.
What are the Side Effects of Raising the Value?
None.
When Should the Value of This Tunable Be Lowered?
The value should be lowered only to limit the number of threads
on the system, or when there is memory pressure and the value of
nkthread
is far above the expected usage.
What are the Side Effects of Lowering the Value?
Increased risk of application failure do to the inability to create
new threads or fork new processes.
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 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
nkthread
was developed by HP.
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