gcstats: GC Statistics for Racket🔗ℹ

Sam Tobin-Hochstadt

The gcstats package provides GC (garbage collection) statistics for Racket programs, similar to GHC’s +RTS -s option.

1 Usage🔗ℹ

To collect GC statistics for a Racket program, use:

racket -l gcstats <normal-racket-arguments>

For example:

racket -l gcstats -t "foo.rkt"

racket -l gcstats -l drracket

When the program exits, gcstats prints a summary of GC activity to standard output.

2,715,625,408 bytes allocated in the heap

2,687,494,428 bytes collected by GC

73,728,640 bytes max heap size

66,748,764 bytes max slop

85,884,928 bytes peak total memory use

Generation 0: 147 collections, 1,120ms, 1,157.53ms elapsed

Generation 1: 6 collections, 596ms, 605.63ms elapsed

INIT time 260 ms

MUT time 8,996 ms ( 9,038.51 ms elapsed)

GC time 1,716 ms ( 1,763.16 ms elapsed)

TOTAL time 10,972 ms ( 11,061.67 ms elapsed)

Max pause time: 123 ms

%GC time 16.02 % ( 16.32 % elapsed)

Alloc rate 301,870,321 bytes per MUT second

bytes allocated in the heap — Total bytes allocated by the program.
bytes collected by GC — Total bytes reclaimed during garbage collection.
bytes max heap size — Largest heap size observed at any GC.
bytes max slop — Largest difference between memory allocated and memory the GC has reserved.
bytes peak total memory use — Largest total memory use, including GC overhead.

Generation 0 — Nursery (minor) collections: count and time in both process and elapsed time.
Generation 1 — Major collections: count and time in both process and elapsed time.
Incremental — Incremental collections (if any): count and time. This line only appears if incremental collections occurred.

INIT time — Time spent before logging started, primarily Racket startup and code loading.
MUT time — Time the “mutator” (your program) was running, excluding GC.
GC time — Total time spent in garbage collection.
TOTAL time — Total time from initial invocation.
Max pause time — Longest individual GC pause.
%GC time — Percentage of time (after initialization) spent in GC.
Alloc rate — Average allocation rate in bytes per second of mutator time.