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gh-112532: Use separate mimalloc heaps for GC objects (gh-113263)

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* gh-112532: Use separate mimalloc heaps for GC objects

In `--disable-gil` builds, we now use four separate heaps in
anticipation of using mimalloc to find GC objects when the GIL is
disabled. To support this, we also make a few changes to mimalloc:

* `mi_heap_t` and `mi_tld_t` initialization is split from allocation.
  This allows us to have a `mi_tld_t` per-`PyThreadState`, which is
  important to keep interpreter isolation, since the same OS thread may
  run in multiple interpreters (using different PyThreadStates.)

* Heap abandoning (mi_heap_collect_ex) can now be called from a
  different thread than the one that created the heap. This is necessary
  because we may clear and delete the containing PyThreadStates from a
  different thread during finalization and after fork().

* Use enum instead of defines and guard mimalloc includes.

* The enum typedef will be convenient for future PRs that use the type.
* Guarding the mimalloc includes allows us to unconditionally include
  pycore_mimalloc.h from other header files that rely on things like
  `struct _mimalloc_thread_state`.

* Only define _mimalloc_thread_state in Py_GIL_DISABLED builds
This commit is contained in:
Sam Gross 2023-12-26 11:53:20 -05:00 • committed by GitHub
parent 8f5b998706
commit acf3bcc886
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9 changed files with 163 additions and 25 deletions
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33
Objects/mimalloc/heap.c
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@ -123,6 +123,9 @@ static void mi_heap_collect_ex(mi_heap_t* heap, mi_collect_t collect)
const bool force = collect >= MI_FORCE;
_mi_deferred_free(heap, force);
// gh-112532: we may be called from a thread that is not the owner of the heap
bool is_main_thread = _mi_is_main_thread() && heap->thread_id == _mi_thread_id();
// note: never reclaim on collect but leave it to threads that need storage to reclaim
const bool force_main =
#ifdef NDEBUG
@ -130,7 +133,7 @@ static void mi_heap_collect_ex(mi_heap_t* heap, mi_collect_t collect)
#else
collect >= MI_FORCE
#endif
&& _mi_is_main_thread() && mi_heap_is_backing(heap) && !heap->no_reclaim;
&& is_main_thread && mi_heap_is_backing(heap) && !heap->no_reclaim;
if (force_main) {
// the main thread is abandoned (end-of-program), try to reclaim all abandoned segments.
@ -164,7 +167,7 @@ static void mi_heap_collect_ex(mi_heap_t* heap, mi_collect_t collect)
}
// collect regions on program-exit (or shared library unload)
if (force && _mi_is_main_thread() && mi_heap_is_backing(heap)) {
if (force && is_main_thread && mi_heap_is_backing(heap)) {
_mi_thread_data_collect(); // collect thread data cache
_mi_arena_collect(true /* force purge */, &heap->tld->stats);
}
@ -206,18 +209,28 @@ mi_heap_t* mi_heap_get_backing(void) {
return bheap;
}
void _mi_heap_init_ex(mi_heap_t* heap, mi_tld_t* tld, mi_arena_id_t arena_id)
{
_mi_memcpy_aligned(heap, &_mi_heap_empty, sizeof(mi_heap_t));
heap->tld = tld;
heap->thread_id = _mi_thread_id();
heap->arena_id = arena_id;
if (heap == tld->heap_backing) {
_mi_random_init(&heap->random);
}
else {
_mi_random_split(&tld->heap_backing->random, &heap->random);
}
heap->cookie = _mi_heap_random_next(heap) | 1;
heap->keys[0] = _mi_heap_random_next(heap);
heap->keys[1] = _mi_heap_random_next(heap);
}
mi_decl_nodiscard mi_heap_t* mi_heap_new_in_arena(mi_arena_id_t arena_id) {
mi_heap_t* bheap = mi_heap_get_backing();
mi_heap_t* heap = mi_heap_malloc_tp(bheap, mi_heap_t); // todo: OS allocate in secure mode?
if (heap == NULL) return NULL;
_mi_memcpy_aligned(heap, &_mi_heap_empty, sizeof(mi_heap_t));
heap->tld = bheap->tld;
heap->thread_id = _mi_thread_id();
heap->arena_id = arena_id;
_mi_random_split(&bheap->random, &heap->random);
heap->cookie = _mi_heap_random_next(heap) | 1;
heap->keys[0] = _mi_heap_random_next(heap);
heap->keys[1] = _mi_heap_random_next(heap);
_mi_heap_init_ex(heap, bheap->tld, arena_id);
heap->no_reclaim = true; // don't reclaim abandoned pages or otherwise destroy is unsafe
// push on the thread local heaps list
heap->next = heap->tld->heaps;