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HP-UX Virtual Partitions Administrator’s Guide > Appendix B Problem with Adding Unbound CPUs to a Virtual Partition (A.03.xx)

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When a virtual partition boots, the HP-UX kernel creates a table of the existing unbound CPUs available at the time the virtual partition is booted. If there is not an existing entry in the table for a specific CPU, that CPU cannot be added to the partition.

Example

To simplify the example, this appendix uses a generic eight-way (8-CPU) server whose CPUs are at the hypothetical hardware paths of x01, x02, x03, x04, x05, x06, x07, and x08.

Create the Virtual Partitions

Suppose we create three partitions using the following commands.

# vparcreate -p vpar1 -a cpu::2 -a cpu:::2 # vparcreate -p vpar2 -a cpu::2 -a cpu:::2 # vparcreate -p vpar3 -a cpu::1

And suppose that the vPars Monitor chooses the following hardware paths for the bound CPUs:

Virtual Partition

vpar1

vpar2

vpar3

Paths of Bound CPU(s)

x01

x02

x03

x04

x05

This configuration leaves the following three CPUs as unbound CPUs:

Paths of Unbound CPUs

x06, x07, x08

Boot the Virtual Partitions

When we boot the partitions, they will boot with the following bound CPUs; their respective kernels will have the following unbound CPU entries.

Note that the entries for the unbound CPUs are only entries for unbound CPUs that can potentially be added to the partition. At this point, we have not assigned any unbound CPUs to any of the partitions:

Virtual Partition

vpar1

vpar2

vpar3

Paths of Bound CPU(s)

x01

x02

x03

x04

x05

Unbound CPU Kernel Entries

x06

x07

x08

x06

x07

x08

x06

x07

x08

Paths of Unbound CPUs

x06, x07, x08

Looking at vpar3, because kernel entries for CPUs at x06, x07, and x08 exist, any of the unbound CPUs (x06, x07, or x08) can be added to vpar3. They could also be added to vpar1 or vpar2.

Create A Fourth Virtual Partition

Supposed we create and boot a fourth partition using the following command:

# vparcreate -p vpar4 -a cpu::3 -a cpu:::3

The vPars Monitor will assign the remaining three CPUs at hardware paths x06, x07, and x08:

Virtual Partition

vpar4

Paths of Bound CPU(s)

x06

x07

x08

Unbound CPU Kernel Entries

(none)

Remove a Virtual Partition

If we shutdown and remove vpar2 (using vparremove), its bound CPUs will become unbound, and the current configuration will be the following:

Virtual Partition

vpar1

vpar3

vpar4

Paths of Bound CPU(s)

x01

x02

x05

x06

x07

x08

Unbound CPU Kernel Entries

x06

x07

x08

x06

x07

x08

(none)

Paths of Unbound CPUs

unbound CPUs are now at x03 and x04

There are now two unbound CPUs, but these CPUs are not the same ones that were available at the time the partitions vpar1 or vpar3 were booted.

Problem is Encountered

At this point, if we attempt to add an unbound CPU to vpar3 using the following command:

# vparmodify -p vpar3 -a cpu::1

the command will fail and return the error message:

vparmodify Error: “-a cpu::1”: One or more unbound CPUs were not available when virtual partition vpar3 was booted. You must shutdown the partition to add them.

Although two unbound CPUs are available, their hardware paths are x03 and x04. But the kernel entries for vpar3 are x06, x07, and x08. Therefore, the command will fail.

The Workaround: Reboot the Target Virtual Partition

Because unbound CPU kernel entries are created when the target partition is booted, you can reboot the target partition so that kernel entries created correctly reflect the available unbound CPUs.

In our example, if we want to add an unbound CPU to vpar3, we can reboot vpar3:

vpar3# vparstatus vpar3# shutdown -r

When vpar3 boots again, its kernel will create the correct entries for the unbound CPUs, which are now at x03 and x04. The configuration becomes:

Virtual Partition

vpar1

vpar3

vpar4

Paths of Bound CPU(s)

x01

x02

x05

x06

x07

x08

Unbound CPU Kernel Entries

x06

x07

x08

x03

x04

(none)

Paths of Unbound CPUs

unbound CPUs are now at x03 and x04

Because the unbound CPUs are at x03 and x04 and the kernel entries for vpar3 are x03 and x04, the command to add an unbound CPU to vpar3

# vparmodify -a vpar3 -a cpu::1

now will be successful.

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