5.5.2. Multiple Shared Processor Pools

There are 64 shared processor pools available on every managed system. Each of the 64 shared processor pools has a unique pool ID (0 to 63) and a name. The pool with pool ID 0 is the so-called default pool. LPARs are assigned to this pool by default if no explicit pool has been assigned. In addition to the default pool, there are 63 other shared processor pools, which have the names SharedPool01, SharedPool02 etc. No further shared processor pools can be created, and none of the 64 shared processor pools can be deleted! Shared processor pools can only be reconfigured. In addition to the name and the unique pool ID, each shared processor pool has 2 configurable attributes:

    • max_pool_proc_units – This attribute defines the so-called maximum pool capacity (MPC). This specifies the maximum number of processing units that can be assigned to the shared processor pool (and thus the assigned LPARs) during a 10 ms interval. The value must be an integer.
    • reserved_pool_proc_units – This attribute can be used to reserve an additional entitlement for a shared processor pool, which can then be used by the assigned LPARs in addition to their guaranteed entitlement. Details will follow later.

The currently used shared processor pools on a managed system can be displayed with “ms lsprocpool” (list processor pools):

$ ms lsprocpool ms11
MS_NAME  PROCPOOL     ID  EC_LPARS  RESERVED  PENDING  ENTITLED  MAX
ms11  DefaultPool  0   1.20      -         -        1.20      -
$

By default, in addition to the default pool, only shared processor pools with a maximum pool capacity greater than 0 are shown. LPARs can only be assigned to these. If all shared processor pools are to be displayed, the “-a” (all) option can be used:

$ ms lsprocpool -a ms11
MS_NAME  PROCPOOL      ID  EC_LPARS  RESERVED  PENDING  ENTITLED  MAX
ms11  DefaultPool   0   1.20      -         -        1.20      -
ms11  SharedPool01  1   0.00      0.00      0.00     0.00      0.00
ms11  SharedPool02  2   0.00      0.00      0.00     0.00      0.00
ms11  SharedPool03  3   0.00      0.00      0.00     0.00      0.00
ms11  SharedPool04  4   0.00      0.00      0.00     0.00      0.00
…
ms11  SharedPool62  62  0.00      0.00      0.00     0.00      0.00
ms11  SharedPool63  63  0.00      0.00      0.00     0.00      0.00
$

Shared processor pools are not a division of the processors in the physical shared processor pool. Shared processor pools should be viewed more as a grouping of LPARs. Each group of LPARs (Shared Processor Pool) has a maximum processor capacity (Maximum Pool Capacity), which defines how many processor shares all LPARs in the group can get together.

Another feature of shared processor pools is the distribution of the guaranteed processor shares of the LPARs in a pool. Portions of the guaranteed entitlement that are not required by an LPAR are first allocated to LPARs in the same shared processor pool. Only if these shares are not used in the same shared processor pool are they returned to the hypervisor and can be distributed to all LPARs (also in other shared processor pools).