This test shows the impact on network throughput when increasing
the inbound buffer count value.
The inbound buffer count is a Linux™ network
interface parameter that can be increased to allow more packets received
in flight, in order to increase throughput. This parameter is defined
per network device individually. The default value is 16.
Figure 1 shows
the impact on transaction throughput when increasing the inbound buffer
count parameter from the default value of 16 to 64 and 128.Figure 1. Impact on transaction throughput
when scaling the inbound network buffer count size
Observation
When increasing the amount of inbound buffers from the default
value of 16 to 64 and then to 128, the throughput degrades for each
step. An inbound buffer count of 64 buffers resulted in a 10% reduction
of transaction throughput. An inbound buffer count of 128 resulted
in an additional 12% reduction of transaction throughput.
Conclusion
The best choice for the test environment of this study is the
default inbound buffer count of 16.
Note: Increasing the inbound buffer
count is typically recommended for optimum network throughput. In
this scenario, the higher network throughput led to a reduced transaction
rate, because it is correlated with an increased cluster contention
and increased communication using the Interconnect needed to maintain
the cache consistency.
