Garbage collection on paging space blocks after a re-pagein
The method of freeing a paging-space disk block after a page has been read back into memory from paging space is employed by default.
The reason that this is not freed up for every re-pagein is because leaving the blocks in paging space provides better performance in the case of unmodified working storage pages that are stolen by the LRU daemon. If pages are stolen, it is not necessary to perform the re-pageout function.
You can tune the following parameters with the vmo command:
Tuning the npsrpgmin parameter:
| Item | Descriptor |
|---|---|
| Purpose: | Specifies the number of free paging space blocks threshold when re-pagein garbage collection starts. |
| Values: | Default: MAX (768, npswarn+ (npswarn/2) |
| Range: | 0 to total number of paging space blocks in the system. |
Tuning the npsrpgax parameter:
| Item | Descriptor |
|---|---|
| Purpose: | Specifies the number of free paging space blocks threshold when re-pagin garbage collection stops. |
| Values: | Default: MAX (1024, npswarn*2) |
Tuning the rpgclean parameter:
| Item | Descriptor |
|---|---|
| Purpose: | Enables or disables the freeing of paging space blocks of pages from the deferred page space allocation policy on read accesses to them. |
| Values: | Default: 0, which signifies free paging space disk blocks only on pagein of pages that are being modified. A value of 1 signifies free paging space disk blocks on pagein of a page being modified or accessed, or read. |
| Range: | 0 | 1 |
Tuning the rpgcontrol parameter:
| Item | Descriptor |
|---|---|
| Purpose: | Enables or disables the freeing of paging space blocks at pagein of pages from the deferred page space allocation policy. |
| Values: | Default:
2, which signifies that it always enables freeing of paging space
disk blocks on pagein, regardless of thresholds. Note: Read accesses
are only processed if the value of the rpgcontrol parameter
is 1. By default, only write accesses are always processed.
A
value of 0 disables freeing of paging space disk blocks on pagein. |
| Range: | 0 | 1 | 2 |