Expand Configuration and Management Manual (H06.03+)

Tuning
Expand Configuration and Management Manual—529522-002
19-18
Multi-CPU Paths
Load Factor Balancing
If there are no matching CPUs, then the load would be distributed based on the load
factor of the paths in the superpath.
If a process on \A in CPU 0 is communicating with a process on \B in CPU 2, the line
handler chosen is based on the load factor of the two lines.
Once the CPU pair has been established, that line handler is used for all
communication between the two CPUs. In an example of CPU 0 to CPU 2 and
assuming that the line handler in CPU 3 is the one chosen, all traffic from CPU 0 to
CPU 2 uses the line handler in CPU 3.
Pair Count Balancing
If the loads are fairly close, the number of CPU pairs using the paths in a superpath is
looked at in determining the connection.
Figure 19-4 depicts the loading for systems that are direct neighbors and are
connected with a superpath, plus connections for non-neighbors:
\A and \B are connected with a superpath, \C is connected to \B, and \D connects to
\C.
Note. The selection algorithm is such that the more loaded line can still be chosen. When a
new connection is being established, the selection algorithm not only looks at the load factor,
but also checks to see if this path has been chosen recently. A loaded path can still be chosen
as the one for a new connection. This way, a single line that looks unused at the time won't get
all of the new connections assigned to it, but they will be distributed over the superpath.
Figure 19-4. Pair Count Balancing for Neighbors and Non-Neighbors
CPU 0
CPU 1
CPU 2
CPU 3
CPU 0
CPU 1
CPU 2
CPU 3
\A \B
\C \D
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