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Partition configuration

 
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Harvey Garner
Occasional Contributor

Partition configuration

During the creation or modification of a npar you are asked to add cell boards to the partion. The last paramter of the add cell command askes about possible memory interleaving. The man page goes on to describe percentages and absolute values that can be put in the parm.

What are the situations that you would want or not want to have memory interleaving? What are the benifits/drawbacks of putting a value in the field. What would be a "good"/"bad" value to use.

It appears that all machines delivered by HP have 0 on all cell boards in the single partition set to 0. Is this a hint to not use the clm_value?

If a value should be used how does one specify it in the genesis partition?
4 REPLIES 4
Michael Steele_2
Honored Contributor

Re: Partition configuration

What server model?

In superdomes don't mix DIMM sizes. Its critical for all DIMMS to have identical sizes and I believe 512MB is the Superdome size. But might be different for other servers. So what server model.

Review this document for a better discussion.
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Michael Steele_2
Honored Contributor

Re: Partition configuration

clm_value = cluster local memory. Verses non-local or shared or memory to be used in interleaving.

See attached parcreate description.

Map out your local and shared / interleaving memory.

'0' (zero) defaults to 100% ov memory used for sharing and interleaving.

"...If no clm_value is specified, maximum interleaved memory (no CLM) is assumed for cells...".

Since 0 (zero) is the default, I'd accept it.
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Michael Steele_2
Honored Contributor

Re: Partition configuration

clm_value = cell local memory.
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Stefan Stechemesser
Honored Contributor
Solution

Re: Partition configuration

Hi,

if a CPU want to access memory, it is faster to get the memory from the same cell as the CPU (local memory) as from other cells (memory traffic goes through the backplane).
This means that you have different latencies when accessing memory dependent of where the memory is located.
Interleaving has the advantage that this latency is constant, because each cache line is distributed on all cells.
HPUX 11.23 provides the funcionality that the programmer can better control the memory usage. If the application supports it, you can have some performance advantage if your process is only using memory from the same cell. Of course, this should only be done, if 1.) all threads that use this memory are running on the same cell and 2.) the memory on that cell is sufficient. If the process uses additional memory from other cells, this would slow down the application.
HPUX 11.23 by default tries to use local memory first if appropiate and available.
See HPUX 11.23 Release Notes for more details on this.

http://docs.hp.com/en/5990-6737/ch11s02.html?jumpid=reg_R1002_USEN

Attention: Do not use Cell local Memory on a HPUX 11.11 system. The memory would be invisible to the Operating System.

best regards

Stefan