HP-UX Virtual Partitions Administrator's Guide (includes A.03.05 and A.04.05)

setboot -m on|off
For more information on using or setting HT ON/OFF, see the nPartition Administrator's
Guide.
• Although hyperthreading is supported within vPars, CPU assignments to virtual partitions
remain on a per-core basis and not on a logical CPU (LCPU) basis.
This means that all the vPars commands for CPUs work the same as they did in vPars A.04.xx,
including using the same legacy hardware path format.
• HT ON is not supported in a mixed HP-UX 11i v2/v3 vPars environment.
• Turning hyperthreading on or off at the EFI level or Monitor level has nPar wide scope.
Individual virtual partitions can use the HP-UX command lcpu_attr to turn logical
processors on or off within processor sets in a virtual partition. However, if hyperthreading
is turned off at the EFI or Monitor level, the lcpu_attr command will not have any effect.
CPUs: Managing I/O Interrupts
This section describes information you need if you are managing I/O interrupts on a vPars-enabled
system. Note that migrating interrupts should only be done by advanced administrators for
performance tuning.
intctl command
The intctl command is a HP-UX tool that allows you to manage I/O interrupts among active
CPUs.
For HP-UX 11i v2 and later, the software for intctl is part of the Core OS.
For more information, see the Interrupt Migration Product Note available at http://docs.hp.com or
see the intctl(1M) manpage.
Notes
• At boot time of a virtual partition, interrupts are processed by all the CPUs in the virtual
partition.
• After boot, CPUs that are added to the virtual partition are not assigned to process I/O
interrupts. However, you can migrate I/O interrupts to any added CPU using intctl.
• After boot, CPUs that are deleted from a virtual partition no longer process I/O interrupts
for the partition. When a CPU is deleted from a virtual partition, if the deleted CPU has I/O
interrupts, the I/O interrupts are automatically and transparently reassigned to other active
CPUs in the partition.
NOTE: Repeatedly adding and deleting CPUs without a reboot of the target virtual partition
may cause an imbalance in the interrupt processing load across the CPUs of the virtual partition.
However, you can use intctl to rectify the imbalance if necessary.
CPUs: Managing I/O Interrupts 203