Tuning example: CPU and I/O saturation

One experiment on a CPU-bound query found near-linear scaling in performance by adding CPUs until the I/O subsystem became saturated. At that point, additional CPU resources did not improve performance. The query performs a table scan on an 800MB table with 30 partitions, using 16K I/O. Table 7-3 shows the CPU scaling.

Table 7-3: Scaling of engines and worker processes

Engines

Elapsed time, (in seconds)

CPU utilization

I/O saturation

Throughput per device, per second

1

207

100%

Not saturated

.13MB

2

100

98.7%

Not saturated

.27MB

4

50

98%

Not saturated

.53MB

8

27

93%

100% saturated

.99MB