Table of Content
4. 아래와 같은 경우에는 memory free 영역이 남아있더라도 unexpected pgsp out이 발생할수 있습니다.
AIX 6.1 Default memory tuning
- minperm = 3%
- maxperm = 90%
- maxclient = 90%
- lru_file_repage = 0
This will prevent paging unless avm > 95% of RAM
Exceptional cases with the above tuning
- PSALLOC=EARLY
- Causes paging space to be allocated when memory is allocated
- Standard behavior prior to AIX 4.3
- Some application recommend this to guarantee paging allocation
- Identify via env variables: use
getevars
in perfpmr package
- Workload Manager
- Workload manager can be used to restrict a class’s virtual memory usage
- When limits hit, paging space used regardless of other settings
- WLM config provided in config.sum
- Memory pools, prior to 5.3.0.41
- Unbalanced memory pools may cause paging activity
- Kernel changes should prevent this from occurring
- Memory_affinity should not be disabled unless recommended
- Free list reaches 0
- If free list reaches 0 within a memory pool, system may page regardless of memory usage
- To resolve this,
1) increase minfree/maxfree so LRU starts earlier
2) use List Based LRU algorithm by changing
page_steal_method
from 0 (default) to 1 (requires reboot) - 64KB page exhaustion
In certain cases, the psmd daemon may page out 64KB pages rather than freeing file cache pages
AIX 5.3 TL8 APAR IZ15692
AIX 5.3 TL9 APAR IZ08649
AIX 6.1 TL1 APAR IZ17835
- 64K PAGING TAKING PLACE WHEN AVAILABLE SYSTEM RAM EXISTS
Defect# 735156 (APAR IZ67445,IZ68083)
When using 64k pages there may be paging space page outs of 64k pages even when VMM tuning indicates it
should not be happening and AVM << real memory. This will normally occur when the demand for 64k and 4k pages is fluctuating. - DEFECTs
- PSMD OPERATIONS ARE VERY SLOW
Very slow system operation when PSMD is in operation while a particular page size pool has been exhausted but another remains available for page size promotion or demotion. - 5300-08 – use AIX APAR IZ46113
- 5300-09 – use AIX APAR IZ46013
- 6100-02 – use AIX APAR IZ42626