Dear GHC (pre-4.07-i386-unknown-linux),
I am going to use the profiling to measure the parts of certain
large program. To understand things, I start with simple example:
main =
let lgft :: Integer -> Int
lgft n = _scc_ "length n!" (length $ show $ product [2..n])
ls = map lgft [2..500] :: [Int]
s = _scc_ "sum" (sum [1..22000] :: Integer)
in
putStr $ shows (s,ls) "\n"
---------------------------------------------
ghc -c -O -prof T.hs; ghc -o -prof run T.o; run +RTS -pT
gives run.prof:
---------------------------------------------------
total time = 3.60 secs (180 ticks @ 20 ms)
total alloc = 139,166,388 bytes (excludes profiling overheads)
COST CENTRE MODULE %time %alloc
length n! Main 99.4 99.3
GC GC 24.4 0.0
individual inherited
COST CENTRE MODULE entries %time %alloc %time %alloc
MAIN MAIN 0 0.0 0.0 100.0 100.0
CAF PrelHandle 3 0.0 0.0 0.0 0.0
CAF Main 3 0.0 0.0 100.0 100.0
length n! Main 499 99.4 99.3 99.4 99.3
sum Main 1 0.6 0.7 0.6 0.7
-----------------------------------------------------------------
What does this mean CAF ?
The last two lines of the second table show that 0.994 of time and
0.993 of allocations was spent by the center "length n!".
This looks natural.
But what means the first table? Why "sum" is skipped there?
Does it show that the Garbage Collection has taken 0.244 of the
total time?
GC can be caused by many values. To find out which part of GC is
caused by the given item f, we have to look at the %alloc part for
f in the second table.
Could you please tell me whether I understand these things correct?
Thank you.
------------------
Sergey Mechveliani
[EMAIL PROTECTED]
