HPVM dynamic memory won't resize

[Rike255]

Hello,

I have a VM Guest (HPVM 4.2.5) configured as follows:

[Memory Details]
Total memory : 32 GB
Minimum memory limit : 512 MB
Maximum memory limit : 64 GB
Reserved memory : 64 MB
Minimum reserved limit : 32 MB
Maximum reserved limit : 64 GB
VHPT Size : 1 MB

[Dynamic Memory Information]
Type : driver
Minimum memory : 1024 MB
Target memory : 30778 MB
Memory entitlement : Not specified
Maximum memory : 32768 MB
Current memory : 32762 MB
Comfortable minimum : 12538 MB
Total memory : 32762 MB
Free memory : 12264 MB
Available memory : 12577 MB
Memory pressure : 0
Memory chunksize : 65536 KB
AMR chunksize : 256 MB
Driver Mode(s) : STARTED ENABLED GUESTCTL
AMR state : DISABLED

When I run an hpvmmodify -x ram_target=30G the command returns no errors and I see the ram target change (shown above), but the memory never decreases.  In the documentation it says it can take a long time if the memory is fragmented, but this guest is doing almost no work and has a lot of memory space available.  

#hpvmmgmt -x ram_target=30G
Attempting to decrease memory from 32762 MB to 30720 MB.
Successfully began to change ram_target to 30720 MB.

# hpvmmgmt -V -l ram
[Dynamic Memory Information]
=======================================
Type : driver
Minimum memory : 1024 MB
Target memory : 30778 MB
Maximum memory : 32768 MB
Current memory : 32762 MB
Comfortable minimum : 12538 MB
Boot memory : 32762 MB
Free memory : 12264 MB
Available memory : 12577 MB
Memory pressure : 0
Memory chunksize : 65536 KB
Driver Mode(s) : STARTED ENABLED GUESTCTL

I waited a good 10 minutes with no changes to the current memory.  I see an error in syslog that says:

vmunix: hpvmdynmem: unable to reach target memory size of 30778 MB after 60 seconds, resulting memory size is 32762 MB.

I can't figure out why I can't resize this VM.  Anyone else run into this?

Thanks,

Ryan

[Dave Olker]

Hi Ryan,

I wonder if this is a situation where the memory on your VM Host has become fragmented.  Looking at the HPVM 4.3 Admin Guide:

8.10.3 Troubleshooting Dynamic Memory Problems

This section describes how to solve problems in the use of dynamic memory.

8.10.3.1 Dynamic Memory Restrictions

• If the virtual machine memory has become fragmented , attempting to reduce the size of the virtual machine might fail or might take a very long time. If you cannot reduce the size the virtual machine might fail or might take a very long time. If you cannot reduce the size of the virtual machine to the desired size, end the operation by setting a new target size.

Are you setting the kctune parameter "base_pagesize" to 64 on your VM Host system?  That can really reduce memory fragmentation issues on the VM Host and help with dynamic memory resizing issues.

Hope this helps,

Dave