NAME
ioforw_timeout — enable timeout in I/O forwarding
VALUES
Allowed values
0 (off)
or
1 (on)
Recommended values
0 (off)
DESCRIPTION
With I/O forwarding, the drivers' strategy routine forwards the
I/O requests to a processor that is configured to handle the I/O
completion interrupts from the device.
I/O forwarding queues these requests in a per processor queue and
handles them in a low priority interrupt context.
In case of large number of requests, I/O forwarding may starve
processes scheduled on the processor.
When the tunable
ioforw_timeout
is set to 1, I/O forwarding times out periodically to let the
processes execute.
This is important when the system has time sensitive processes that may flag an
error condition in the system resulting in the generation of unnecessary
correction triggers.
Since a timeout is introduced in I/O forwarding, there
may be a loss in I/O throughput.
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 Tunable Be Turned On?
This tunable should be turned
on
if a time critical process times out in the presence of heavy I/O.
What Are the Side Effects of Turning the Tunable On?
As the timeout is introduced in I/O forwarding request processing,
I/O throughput of the system may be reduced.
What Other Tunables 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
ioforw_timeout
was developed by HP.
