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intr_strobe_ics_pct(5)

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

intr_strobe_ics_pct was developed by HP.

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