Test Program - xrdopen

This is a C program the uses the xroot API to communicate with an xrootd
or olbd server. The inner loop of this program consists of open(), close(),
open(), close(), read(). The first open incurs the cost of connecting
to the server, but the connection is retained for the second open. The
read() is a one byte read. Before and after each open() and read(), the
gettimeofday() system function is used to measure the latency of the
open() and read() functions. The gettimeofday() function appears to have
a granularity of 1 microsecond. The program returns the latency for the
first open(), second open(), and read() in microseconds.

Outer script - runxrdopen

The outer script invokes the test program 10,000 times, sorts the values
for the first open(), second open(), and read(), and then calculates the
average and median values. To avoid unwanted skewing of the average values,
the highest 1% of the sorted values are discarded.

Test results

The test program was run against the local filesystem on the xrootd
server to measure the operating system cost of opening a file. Then
all combinations of Solaris and Linux clients and xrootd servers were
tested. Finally, the a Solaris olbd was tested with both clients.

All numbers in the following table are in microseconds.

                                      1st Open      2nd Open        Read
                                     Avg Median    Avg Median    Avg Median
Linux local filesystem                13     13      3      3      4      5
Solaris local filesystem              43     42      4      5     18     17
Solaris client -> Linux xrootd      4312   4241    884    862    122    122
Solaris client -> Solaris xrootd    4402   4315    917    895    133    133
Linux client -> Linux xrootd        7568   7544   5378   5329    108    108
Linux client -> Solaris xrootd      7685   7638   5429   5376    118    118
Solaris client -> Solaris olbd      5570   5424   1235   1206    133    132
Linux client -> Solaris olbd       11011  10916   8046   7969    117    117