Lecture 02 Micro-Partition Overview

© Copyright IBM Corporation 2006 Course materials may not be reproduced in whole or in part without written permission of the AIX Collaboration Center3.2

Micro-Partition Overview

© Copyright IBM Corporation – AIX Collaboration Center 2006

IBM System pLPARs are defined to be dedicated or shared

Dedicated partitions use whole number of CPUsShared partitions use whole or fractions of CPUs from Shared Pool

Shared processor pool - subset of physical CPUs in a system all CPUs that are not in dedicated LPARs

Processing capacity for a micro-partition specified in terms of processing units.The smallest capacity that can be specified for a partition is 0.1 Processing units, equivalent to 1/10 of a processorAdditional processing capacity can be configured in fractions of 0.01 processing units.

Configure the following options for processing capacity:Desired: Size of partition at activation, between minimum and desiredMinimum: Partition won’t start if Minimum capacity not availableMaximum: CPU that can’t be exceeded in DLPAR operation

Capped vs uncapped Capped: CPU Capacity limited to ‘desired’ entitlementUncapped: CPU Capacity limited by unused capacity in ‘pool’

LPAR weighting to determine preference when pool cycles are constrainedSome LPARs more favored (up to weight 255), some less favored (down to weight 1)

Shared Processor LPARs – Micro-partitions


IBM System p

Shared processor pool

Processor terminology

Shared processor partitionSMT Off

Shared processor partitionSMT On

Dedicated processor partition

SMT Off

Deconfigured

Inactive (CUoD)

Dedicated

Shared

Virtual

Logical (SMT)

Installed physical processors

Entitled capacity


IBM System p

Understanding min/max/desired resource values

• The desired value for a resource is given to a partition if enough resource is available.

• If there is not enough resource to meet the desired value, then a lower amount is allocated.

• If there is not enough resource to meet the min value, the partition will not start.

• The maximum value is only used as an upper limit for dynamic partitioning operations.


IBM System p

Partition capacity entitlement example• Shared pool has 2.0 processing units available • LPARs activated in sequence• Partition 1 activated

- Min = 1.0, max = 2.0, desired = 1.5- Starts with 1.5 allocated processing units

• Partition 2 activated- Min = 1.0, max = 2.0, desired = 1.0- Does not start

• Partition 3 activated- Min = 0.1, max = 1.0, desired = 0.8- Starts with 0.5 allocated processing units


IBM System p

Capped and uncapped partitions

• Capped partition- Not allowed to exceed its entitlement

• Uncapped partition- Is allowed to exceed its entitlement

• Capacity weight- Used for prioritizing uncapped partitions- Value 0-255- Value of 0 referred to as a “soft cap”


IBM System p

Capped Shared Processor LPAR

Maximum Processor Capacity

Entitled Processor CapacityProcessorCapacityUtilization LPAR Capacity Utilization

Pool Idle Capacity Available

Time

minimum processor capacity

ceded capacity

utilized capacity


IBM System p

Uncapped Shared Processor LPAR

Maximum Processor Capacity

ProcessorCapacityUtilization

Pool Idle Capacity Available

Time

Entitled Processor Capacity

minimum processor capacity

Utilized Capacity

ceded capacity


IBM System p

virtual CPUsplpar 2

virtual CPUsplpar1

DispatchWheel (10ms)

Dispatched

virtual timebase

virtual timebase

virtual timebase

virtual timebase

virtual CPUsplpar 1

virtual timebase

virtual CPUsplpar 4

virtual timebase

virtual CPUsplpar 3

virtual timebase

1.00 unitsphysical CPU

timebase

Virtual Processors

Shared processor conceptspartitions run on virtualprocessorsPartition entitled capacity are divided among the virtual processors in the LPARVirtual processors are dispatched on physicalprocessors

Physicalprocessor

Dispatch Window0 1 2 3 4 5 6 7 8 9 10


IBM System p

Shared Processor PoolVirtual ProcessorsProcessing Units

Specified in partsof a processor

Partition#1 0.5 1 Way 1 Virtual

Processor5

Partition#2 0.5 2 Way

2 VirtualProcessors

Partition#3 1.2 4 Way 4 Virtual

Processors

Hypervisor D

ispatch Cycle

10 milliseconds

10 milliseconds

2.5

3

3 3

3

10 milliseconds

2.5

Capped

Capped

Uncapped

5 5

5 5


IBM System p

Virtual Processors in Shared Processor Pool

• Virtual processors represent concurrent operating system operations• Entitled Capacity (physical cpu) is spread across these virtual processors • Optimal number of virtual processors depends on the workload

- Number of threads- What threads are doing

• Number of virtual processors (Minimum and Desired) is obtained by:- Rounding entitled capacity to next whole number- Example

• Minimum = 0.50 (entitlement) -> 1 virtual processor minimum• Desired = 2.25 (entitlement) -> 3 virtual processors desired

• Maximum number of virtual processors is 10x entitlement- Do you want maximum 0.8 entitled over 8 virtual processors?- Some art, experimentation warranted- Some workloads need more concurrence, some need fewer and more

powerful virtual processors


IBM System p

Understanding capacity allocation – An example

• A workload is run under different configurations.• The size of the shared pool (number of physical processors) is fixed at

16.• The capacity entitlement for the partition is fixed at 9.5.• No other partitions are active.


IBM System p

Uncapped – 16 virtual processors

• 16 virtual processors.• Uncapped.• Can use all available resource.• The workload requires 26 minutes to complete.

Uncapped (16PPs/16VPs/9.5CE)

0

5

10

15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Elapsed time


IBM System p

Uncapped – 12 virtual processors

• 12 virtual processors.• Even though the partition is uncapped, it can only use 12 processing units.• The workload now requires 27 minutes to complete.

Uncapped (16PPs/12VPs/9.5CE)

0

5

10

15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Elapsed time


IBM System p

Capped

• The partition is now capped and resource utilization is limited to the capacity entitlement of 9.5.- Capping limits the amount of time each virtual processor is scheduled.- The workload now requires 28 minutes to complete.

Capped (16PPs/12VPs/9.5E)

0

5

10

15

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Elapses time


IBM System p

Match the following processor terms to the statements that describe them:

Dedicated Shared Capped Uncapped Virtual Logical

These processors cannot be used in Micro-partitions ________

Partitions marked as this may use excess processing capacity in the shared pool ________

There are two of these for each virtual processor if SMT is enabled ________

This type of processor must be configured in whole processor units ________

These processors are configured in processing units as small as one hundredth of a processor ________

Partitions marked as this may use up to their entitled capacity but not more ________

These processor are dispatched in a time-sliced manner onto physical processors by the POWER Hypervisor ________

Checkpoint


IBM System p

Summary

• This chapter covered- Understand Micro-partitions- Demonstrate how it was used to consolidate multiple applications

and increased server utilization

• References- APV on System p5 (Redbook)

• APV on IBM System p5-sg247940.pdf- APV on p5 Servers, Architecture and Performance (Redbook)

• APV Architecture and Performance-sg245768.pdf

Documents

Lecture 02 Micro-Partition Overview