FICON Express2 Channel Performance Version 1.0 - IBM

FICON Express2 Channel Performance Version 1.0
Page 16
Figure 16 is the response time components for the 27k read hit benchmark. Because of the
large 27k block size, CONNECT time is the largest component of the total response time. As
link utilizations (LU) increase, CONNECT time increases first by one tenth of a millisecond,
and then PEND time also increases by one tenth of a millisecond. At 80% LU, both
CONNECT time and PEND time are 0.4ms higher than they were at 10% LU, another
indicator that this workload is in the middle of the two extremes defined by processor limited
workloads such as the 4K bytes per I/O benchmarks and bus or link limited workloads such
as the 6x27K bytes per I/O benchmarks.
response time components for 27K read hits...
27K bytes/io, 100% cu cache hit ratio
2Gbps Link Utilization(LU)
10% LU
20% LU
30% LU
40% LU
50% LU
60% LU
70% LU
80% LU
0 0.5 1 1.5 2
response times in ms
Figure 16
pend
conn
The 32x4k read hit benchmark depicted in Figure 17 is another benchmark that pushes both
the processor and the link to high levels of utilization with the processor slightly higher than
the link utilization. Figure 17 shows the response time components for a 32x4K read hit
benchmark which is a long chain of short blocks. Here CONNECT time is the largest
component since the total data transfer size is 128K bytes per I/O even though the block size
for each CCW is only 4K bytes. Since there is a separate CCW for each of the 4K bytes and
the FICON Express2 channel processor works on each CCW separately, the processor gets
pushed to high utilization levels for this workload. With this benchmark, CONNECT time
starts out at a little over 2ms at 10% FICON Processor utilization (FPU) and increases to over
3ms at 60% FPU, when just under 120MB/sec are being transferred, which represents about
60% link utilization as well.