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Optionally disable hugepages for stacks #4001

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Optionally disable hugepages for stacks #4001

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8 changes: 8 additions & 0 deletions runtime/fiber.c
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,8 @@ uintnat caml_init_main_stack_wsz = 0; /* -Xmain_stack_size= */
uintnat caml_init_thread_stack_wsz = 0; /* -Xthread_stack_size= */
uintnat caml_init_fiber_stack_wsz = 0; /* -Xfiber_stack_size= */

uintnat caml_nohugepage_stacks = 0;

uintnat caml_get_init_stack_wsize (int context)
{
uintnat init_stack_wsize = 0;
Expand Down Expand Up @@ -229,6 +231,12 @@ Caml_inline struct stack_info* alloc_for_stack (mlsize_t wosize)
if (stack == NULL) {
return NULL;
}
#ifdef __linux__
/* On Linux, (optionally) disable *any* hugepage usage for stacks.
(Huge pages are not as beneficial for stacks, because you use the same few
kb over and over again, but can have a significant RAM cost) */
if (caml_nohugepage_stacks) madvise(stack, len, MADV_NOHUGEPAGE);
#endif
// mmap is always expected to return a page-aligned value.
CAMLassert((uintnat)stack % page_size == 0);

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2 changes: 2 additions & 0 deletions runtime/gc_ctrl.c
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Expand Up @@ -58,6 +58,7 @@ extern uintnat caml_pool_min_chunk_bsz; /* see shared_heap.c */
extern uintnat caml_percent_sweep_per_mark; /* see major_gc.c */
extern uintnat caml_gc_pacing_policy; /* see major_gc.c */
extern uintnat caml_gc_overhead_adjustment; /* see major_gc.c */
extern uintnat caml_nohugepage_stacks; /* see fiber.c */

CAMLprim value caml_gc_quick_stat(value v)
{
Expand Down Expand Up @@ -443,6 +444,7 @@ static struct gc_tweak gc_tweaks[] = {
{ "percent_sweep_per_mark", &caml_percent_sweep_per_mark, 0 },
{ "gc_pacing_policy", &caml_gc_pacing_policy, 0 },
{ "gc_overhead_adjustment", &caml_gc_overhead_adjustment, 0 },
{ "nohugepage_stacks", &caml_nohugepage_stacks, 0 },
};

enum {N_GC_TWEAKS = sizeof(gc_tweaks)/sizeof(gc_tweaks[0])};
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