Since Matthew added nice programmatic tools for understanding the
behavior of the GC, I've written a little tool to summarize the GC
behavior of your program. You can find it on GitHub here:
https://github.com/samth/gcstats . To install it, do this:
% git clone git://github.com/samth/gcstats.git
% raco link gcstats
Then you can do this:
% racket -l gcstats -u my-program.rkt
and you get output like this:
39,703,916 bytes allocated in the heap
28,890,688 bytes collected by GC
17,083,432 bytes max heap size
16,604,120 bytes max slop
28,229,632 bytes peak total memory use
Generation 0: 5 collections, 32ms, 31.71ms elapsed
Generation 1: 0 collections, 0ms, 0ms elapsed
INIT time 256 ms
MUT time 132 ms ( 129.98 ms elapsed)
GC time 32 ms ( 31.71 ms elapsed)
TOTAL time 420 ms ( 417.69 ms elapsed)
%GC time 19.51% ( 19.61% elapsed)
Alloc rate 300,787,242 bytes per MUT second
There are a few significant limitations at present:
1. There are a few GCs before the tool starts -- it can't report
anything about them.
2. If you have multiple places, it will do totally the wrong thing.
Fixing this will require a little more information from Racket.
3. The current architecture keeps too much info around during the run
of the program. I hope to fix that soon.
The whole thing is inspired by the similar GHC reporting tools,
documented here:
http://www.haskell.org/ghc/docs/latest/html/users_guide/runtime-control.html#rts-options-gc
. The GHC tools report one more interesting piece of information,
which is how many bytes are copied by the GC. I hope we can get the
information from the Racket GC at some point as well.
--
sam th
sa...@ccs.neu.edu
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