Administering Platform LSF - SAS

Chapter 37
Tuning the Cluster
Comparing LIM load thresholds
To tune LIM load thresholds, compare the output of lsload to the thresholds
reported by lshosts -l.
The lsload and lsmon commands display an asterisk * next to each load
index that exceeds its threshold.
Example For example, consider the following output from lshosts -l and lsload:
% lshosts -l
HOST_NAME: hostD
...
LOAD_THRESHOLDS:
r15s r1m r15m ut pg io ls it tmp swp mem
- 3.5 - - 15 - - - - 2M 1M
HOST_NAME: hostA
...
LOAD_THRESHOLDS:
r15s r1m r15m ut pg io ls it tmp swp mem
- 3.5 - - 15 - - - - 2M 1M
% lsload
HOST_NAME status r15s r1m r15m ut pg ls it tmp swp mem
hostD ok 0.0 0.0 0.0 0% 0.0 6 0 30M 32M 10M
hostA busy 1.9 2.1 1.9 47% *69.6 21 0 38M 96M 60M
In this example:
◆ hostD is ok.
◆ hostA is busy—The pg (paging rate) index is 69.6, above the threshold of
15.
If LIM often reports a host as busy
If LIM often reports a host as busy when the CPU utilization and run queue
lengths are relatively low and the system is responding quickly, the most likely
cause is the paging rate threshold. Try raising the pg threshold.
Different operating systems assign subtly different meanings to the paging rate
statistic, so the threshold needs to be set at different levels for different host
types. In particular, HP-UX systems need to be configured with significantly
higher pg values; try starting at a value of 50.
There is a point of diminishing returns. As the paging rate rises, eventually the
system spends too much time waiting for pages and the CPU utilization
decreases. Paging rate is the factor that most directly affects perceived
interactive response. If a system is paging heavily, it feels very slow.
If interactive jobs slow down response
If you find that interactive jobs slow down system response too much while
LIM still reports your host as ok, reduce the CPU run queue lengths (r15s, r1m,
r15m). Likewise, increase CPU run queue lengths if hosts become busy at low
loads.
Administering Platform LSF 485