This patch adds the sprofdiff tool, which compares two sets of profiling
output files. It sorts processes and symbols by difference in average
number of samples, placing those that took more time on the left first
and those that took more time on the right last. If multiple runs are
combined, a standard deviation is computed and this is used to compute
the significance level, which gives an indication of which differences
are likely to be due to chance.
This tool is run not on the raw profiling files, but on the output of
sprofalyze -d (a new option). Though having to use two tools and an
intermediate file seems a bit awkward, the advantage is that the
original source tree is not needed to resolve the symbols. For
comparisons, this is very useful. Also, the intermediate file is in a
text format that can easily be processed by scripts, which may be useful
for other purposes as well.