Hi Johnny, On Thu, Feb 20, 2014 at 5:37 PM, Johnny Billquist wrote:

Are you saying that you essentially avoid GC by creating a large fresh heap every time you call something written in Haskell, and then delete the heap when the Haskell function returns? And that the current piece of code running in Haskell is short enough that GC never is done?

No, does not delete. Pool it. See following code compiled by Ajhc. Ajhc compile Haskell code into C code. https://gist.github.com/master-q/9109334 Please note auichIntr() function that is entry point C => Haskell. https://gist.github.com/master-q/9109334#file-hsmain-c-L2051 int auichIntr(HsPtr x272) { arena_t arena; gc_t gc; gc = NULL; arena = NULL; jhc_alloc_init(&gc,&arena); jhc_hs_init(gc,arena); int x273 = ((int)fFE$__CCall_auichIntr(gc,arena,(uintptr_t)x272)); jhc_alloc_fini(gc,arena); return x273; } The code post-calls jhc_alloc_fini() that pool Haskell heap (named megablock) into free_megablocks. https://github.com/ajhc/ajhc/blob/d93468e34f4514209048d4a92b1549e079ccd3fb/r... void jhc_alloc_fini(gc_t gc,arena_t arena) { -- snip -- SLIST_FOREACH(pg, &arena->monolithic_blocks, link) { SLIST_INSERT_HEAD(&free_monolithic_blocks, pg, link); } SLIST_FOREACH(mb, &arena->megablocks, next) { SLIST_INSERT_HEAD(&free_megablocks, mb, next); } if(arena->current_megablock) { SLIST_INSERT_HEAD(&free_megablocks, arena->current_megablock, next); } Also s_alloc(), Haskell heap allocator, try to get Haskell heap from the pool. If not found, it posix_memalign new megablock. https://github.com/ajhc/ajhc/blob/d93468e34f4514209048d4a92b1549e079ccd3fb/r... struct s_megablock * s_new_megablock(arena_t arena) { jhc_rts_lock(); struct s_megablock *mb = SLIST_FIRST(&free_megablocks); if (mb) { SLIST_REMOVE(&free_megablocks, mb, s_megablock, next); } else { mb = malloc(sizeof(*mb)); #ifdef _JHC_JGC_LIMITED_NUM_MEGABLOCK static int count = 0; if (count >= _JHC_JGC_LIMITED_NUM_MEGABLOCK) { abort(); } mb->base = aligned_megablock + (MEGABLOCK_SIZE) * count; count++; #else mb->base = jhc_aligned_alloc(MEGABLOCK_SIZE); #endif Regards, -- Kiwamu Okabe