intr_strobe_ics_pct.5 (2010 09)

i
intr_strobe_ics_pct(5) intr_strobe_ics_pct(5)
(Tunable Kernel Parameters)
NAME
intr_strobe_ics_pct - limit for the percent of time a processor is allowed to spend in interrupt context
VALUES
Failsafe
100
Default
80
Allowed values
80 - 100
Setting intr_strobe_ics_pct
to 100 will switch the feature off.
Recommended values
100
DESCRIPTION
intr_strobe_ics_pct
specifies the system limit for the percent of time a processor is allowed to
spend in interrupt context. When the tunable is set to a value less than
100, the kernel does not allow
I/O interrupts to consume the processor time beyond the set limit and hence the threads and other low
priority interrupts get time to execute. This is important when the system is under a heavy I/O interrupt
load and some threads like heartbeat timer in service guard environment need to run within a limited
time delay.
In the normal working of the system, the value of the tunable
intr_strobe_ics_pct
should be 80.
If
intr_strobe_ics_pct
is to less than 100, a message like the following may be seen in the mes-
sage buffer.
An interrupt context threshold of #% was exceeded on processor # within
the last # minutes. The current value is #.
The message buffer can be read via dmesg or syslog. This message indicates that the percent of time
spent on the processor crossed the specified limit and corrective action has been taken.
Who Is Expected to Change This Tunable?
Only HP Field engineers should change the value of this tunable.
Restrictions on Changing
Changes to this tunable take effect immediately.
When Should the Value of This Tunable Be Lowered?
The value should be lowered only when heavy I/O interrupt load is causing a time critical process to
timeout.
What Are the Side Effects of Lowering the Value?
Reducing the value of the tunable would give the thread context more time to execute. However, the
overall system throughput may decrease.
What Other Tunable Values Should Be Changed at the Same Time?
This tunable is independent of other tunables.
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.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1