Originally posted by: GK8T_Wojciech_Porwol

Hello,

I have problem with CPU utilization on one LPAR. 

LPAR utilize only 6 phys. cpu up to entitled capacity limit, but form configuration point of view it could be use all cpu in pool.

This is my lparstat restult:

Node Name                                  : rk075
Partition Name                             : rk075
Partition Number                           : 18
Type                                       : Shared-SMT-8
Mode                                       : Uncapped
Entitled Capacity                          : 6.00
Partition Group-ID                         : 32786
Shared Pool ID                             : 3
Online Virtual CPUs                        : 6
Maximum Virtual CPUs                       : 13
Minimum Virtual CPUs                       : 1
Online Memory                              : 194816 MB
Maximum Memory                             : 270592 MB
Minimum Memory                             : 4096 MB
Variable Capacity Weight                   : 200
Minimum Capacity                           : 0.30
Maximum Capacity                           : 13.00
Capacity Increment                         : 0.01
Maximum Physical CPUs in system            : 40
Active Physical CPUs in system             : 32
Active CPUs in Pool                        : 13
Shared Physical CPUs in system             : 32
Maximum Capacity of Pool                   : 1300
Entitled Capacity of Pool                  : 1200
Unallocated Capacity                       : 0.00
Physical CPU Percentage                    : 100.00%
Unallocated Weight                         : 0
Memory Mode                                : Dedicated
Total I/O Memory Entitlement               : -
Variable Memory Capacity Weight            : -
Memory Pool ID                             : -
Physical Memory in the Pool                : -
Hypervisor Page Size                       : -
Unallocated Variable Memory Capacity Weight: -
Unallocated I/O Memory entitlement         : -
Memory Group ID of LPAR                    : -
Desired Virtual CPUs                       : 6
Desired Memory                             : 194816 MB
Desired Variable Capacity Weight           : 200
Desired Capacity                           : 6.00
Target Memory Expansion Factor             : -
Target Memory Expansion Size               : -
Power Saving Mode                          : Disabled
Sub Processor Mode                         : -

Topas show me that LPAR not exceed 6 phys cpu and entc% never show more then 100%.

Strange because on another LPAR on the same CPU pool it works ok, and in high utilization time LPAR use up to defined maximum capacity.

Regards

Wojtek Porwol

Originally posted by: The_Doctor

Sorry, from your description, I'm not seeing a problem.  Your system is behaving exactly like you have it configured.

Topas show me that LPAR not exceed 6 phys cpu and entc% never show more then 100%.

This is to be expected with only 6 online virtual cpus:

Online Virtual CPUs                        : 6

Your sub-pool has:

Active CPUs in Pool                        : 13

But this LPAR will never use the other 7 CPUs in the pool..... with only 6 VPs allocated.  You've effectively "capped" this LPAR with VP=6.

Allocate, say VPs=8 to this LPAR, and see what happens.  If your LPAR has the demand, and the sub-pool still has the spare capacity available, you should see TOPAS report on the "extra" usage.

Originally posted by: GK8T_Wojciech_Porwol

Hi,

Thanks for your answer. Maybe my description wasn't quite clear, but I still see load on 99-100% entitle capacity, and I conclude system is overload now, In my experience when system is overload and when CPUs in configured in uncapped mode, LAPR should be use more then 6 CPUs. Now looks like LPAR is configured in capped mode, with limitation to 6 CPU, like I said another lape on the same CPU pool with similar configuration in the same time could use more then desired capacity. Unfortunaltely I haven't access to HMC and I can based only lparstat commmad. 

Regards

WP

Originally posted by: luverofpeanuts

The Doctor's response is accurate and seems consistent with what you are describing and what the LPARSTAT output shows.  

With 6 online VP's, and the entitled capacity set to 6, your LPAR will be limited to using 6 CPU's, 6 processing units; as such,  TOPAS will never show more than 100% usage.  If you have determined the system is overloaded, you need to add more VP's as the Doctor suggested.  VP's are not added/removed *automatically* as the system needs.   They can be added/removed dynamically (with no reboot), within the range of the min/max VP settings.  That is done by the system administrator via the HMC (or equivalent management device).  

Originally posted by: GK8T_Wojciech_Porwol

Please look on lparstat from two systems:

First %entc more the 100%

System configuration: type=Shared mode=Uncapped smt=4 lcpu=12 mem=32768MB psize=5 ent=2.00  

%user  %sys  %wait  %idle physc %entc  lbusy  vcsw phint  %nsp  %utcyc
----- ----- ------ ------ ----- ----- ------ ----- ----- -----  ------
54.0   5.8    1.8   38.4  2.05 102.4   23.1  8466     0   101   1.21  
54.3   6.9    3.8   35.0  2.14 107.0   26.6  9698     0   101   1.21  
63.6   5.5    1.9   28.9  2.30 114.9   36.8  8311     0   101   1.21  
66.2   4.0    1.5   28.3  2.39 119.5   45.3  7001     0   101   1.21  
57.6   6.1    2.4   33.8  2.18 109.2   28.8  8511     0   101   1.21  
57.6   5.7    2.4   34.3  2.26 113.2   29.7  7715     0   101   1.21  
56.2   6.2    2.4   35.3  2.14 106.9   26.5  8441     0   101   1.21  
56.1   5.8    1.7   36.4  2.17 108.7   27.7  7632     0   101   1.21

and mentioned system:

System configuration: type=Shared mode=Uncapped smt=8 lcpu=48 mem=194816MB psize=13 ent=6.00  

%user  %sys  %wait  %idle physc %entc  lbusy  vcsw phint  %nsp  %utcyc
----- ----- ------ ------ ----- ----- ------ ----- ----- -----  ------
67.7  15.6    4.3   12.3  5.91  98.6   44.4 34219     0   101   0.73  
66.2  16.0    3.4   14.4  5.95  99.2   41.4 28648     0   101   0.73  
65.9  15.4    4.0   14.6  5.95  99.1   41.4 30617     0   101   0.73  
66.0  16.1    3.8   14.1  5.94  98.9   41.7 31656     0   101   0.73  
64.6  14.5    4.5   16.4  5.88  97.9   37.8 31243     0   101   0.73  
60.0  14.6    4.5   20.9  5.77  96.1   34.2 31786     0   101   0.73  
63.7  14.9    4.6   16.7  5.86  97.6   37.3 30126     0   101   0.73  
64.7  15.3    4.6   15.3  5.91  98.5   39.0 32132     0   101   0.73

Like you see, system could use more then desired CPU if CPU pool have free resources at the moment.

Regards

WP

Originally posted by: luverofpeanuts

In the first system, the entitlement is set to 2.0, and the VP's are set to 3, correct?  In an uncapped mode, and with available cpu in the pool, that LPAR will use up 3.0 processing units... thus showing ent% more than 100%.    

In the second system, the entitlement is set to 6.0, the VPs are set to 6.   In uncapped mode, even with available cpu in the pool, that LPAR will not use more than 6.0 processing units, thus, will never get above 100%.   That is by definition of how uncapped partitions work.   So, in the second system, the behavior you expect, is not correct.   That is not how it works.  "uncapped" is only "uncapped" up to number of processing units available to the number of virtual CPU's assigned to the LPAR.    

It seems there is free CPU available in the pool, but in order access that free CPU, you need to add a VP to this second system via that HMC.  Just try it.  If your system is cpu hungry, your entitlement usage will go above 100%.  

Originally posted by: GK8T_Wojciech_Porwol

Yes, you right from first answer, my mistake, this is problem with online VCP

Sorry sometimes I'm dummy :)

Originally posted by: luverofpeanuts

It's easy to miss that limit on uncapped partitions.  Especially since it is really a best practice (from a raw performance perspective) to try to keep your number of VP's allocated to close to the entitlement you need.     Have a great week!