This module provides simple performance measurement for an application. It samples the program counter roughly every 50 microseconds and builds a histogram of the values that it finds. Since there is only a small amount
of memory to store the histogram, the user can specify which area of code is of interest. The default is the entire flash which contains code. Once the hotspots are identified, then the run can then be repeated with different areas and at different resolutions to get as much information as required.
-`total` The total number of samples captured in this run
-`outside` The number of samples that were outside the histogram range
-`histogram` The histogram represented as a table indexed by address where the value is the number of samples. The address is the lowest address for the bin.
-`binsize` The number of bytes per histogram bin.
### Example
perf.start()
for j = 0, 100 do
str = "str"..j
end
tot, out, tbl, binsize = perf.stop()
print(tot, out)
local keyset = {}
local n = 0
for k,v in pairs(tbl) do
n=n+1
keyset[n]=k
end
table.sort(keyset)
for kk,k in ipairs(keyset) do print(string.format("%x - %x",k, k + binsize - 1),tbl[k]) end
This runs a loop creating strings 100 times and then prints out the histogram (after sorting it).
This takes around 2,500 samples and provides a good indication of where all the CPU time is
