I did a fairly through review of the thread-creation and thread-join code in the git master branch, and it looks to be just fine. Thus, some experimentation is in order:
Going back to guile-2.0, I see this behavior: guile -v guile (GNU Guile) 2.0.11 Packaged by Debian (2.0.11-deb+1-10) If I add a manual gc to the exit of the thread, like so: (define (mkthr v) (call-with-new-thread (lambda () (set! junk (+ junk 1)) (gc) ))) then the heap blows up, in minutes, to about 180MB but then stops growing, even after hours and millions of thread creates: (heap-size . 183734272) (gc-times . 1957954) If I gc only every third thread create, it quickly blows up to about 400MB, and then stablizes, for hours: (heap-size . 428638208) (gc-times . 1292663) If I gc every 17th thread, it blows up to about 1.8GB and then is stable: (heap-size . 1875902464) (gc-times . 327462) This last one after about 5.5 million thread creates and joins. The counting is done like so: (define (mkthr v) (call-with-new-thread (lambda () (lock-mutex mtx) (if (eq? 0 (modulo junk 17)) (gc)) (set! junk (+ junk 1)) (unlock-mutex mtx) ))) In each case, it seems to hit a plateau at about (n+1)*100MB when gc is done on one out of every n threads. This seems quite bizarre to me: why does this inverted relation on number of gcs vs number of thread creates? What's magic about 100MB? Clearly 100MB is wayyy too large for this very simple program. I mean, even if I gc at *every* thread-exit ... (I have not yet explored above in guile-2.2) Since I cannot find any 'obvious' bugs in guile, this suggests some strange stochastic behavior in bdw-gc?