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clarify control flow and comments in page reclaim_on_free

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daanx 2025-02-05 16:01:45 -08:00
parent 5aa679cdee
commit 1657bfb453
1 changed files with 18 additions and 18 deletions
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22
src/free.c
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@ -217,17 +217,13 @@ static void mi_decl_noinline mi_free_try_collect_mt(mi_page_t* page, mi_block_t*
return; return;
} }
// 2. if the page is not too full, we can try to reclaim it for ourselves // 2. we can try to reclaim the page for ourselves
// note: // note: we only reclaim if the page originated from our heap (the heap field is preserved on abandonment)
// we only reclaim if the page originated from our heap (the heap field is preserved on abandonment) // to avoid claiming arbitrary object sizes and limit indefinite expansion. This helps benchmarks like `larson`
// to avoid claiming arbitrary object sizes and limit indefinite expansion.
// this helps benchmarks like `larson`
const long reclaim_on_free = _mi_option_get_fast(mi_option_page_reclaim_on_free); const long reclaim_on_free = _mi_option_get_fast(mi_option_page_reclaim_on_free);
if (reclaim_on_free >= 0 && page->block_size <= MI_SMALL_MAX_OBJ_SIZE) // only for small sized blocks if (reclaim_on_free >= 0 && page->block_size <= MI_SMALL_MAX_OBJ_SIZE) // only for small sized blocks
{ {
// the page has still some blocks in use (but not too many) // get our heap (with the right tag)
// reclaim in our heap if compatible, or otherwise abandon again
// todo: optimize this check further?
// note: don't use `mi_heap_get_default()` as we may just have terminated this thread and we should // note: don't use `mi_heap_get_default()` as we may just have terminated this thread and we should
// not reinitialize the heap for this thread. (can happen due to thread-local destructors for example -- issue #944) // not reinitialize the heap for this thread. (can happen due to thread-local destructors for example -- issue #944)
mi_heap_t* heap = mi_prim_get_default_heap(); mi_heap_t* heap = mi_prim_get_default_heap();
@ -236,9 +232,12 @@ static void mi_decl_noinline mi_free_try_collect_mt(mi_page_t* page, mi_block_t*
heap = _mi_heap_by_tag(heap, page->heap_tag); heap = _mi_heap_by_tag(heap, page->heap_tag);
} }
} }
if (heap != NULL && heap->allow_page_reclaim && // can we reclaim?
(heap == page->heap || (reclaim_on_free == 1 && !mi_page_is_used_at_frac(page, 8))) && // only reclaim if we were the originating heap, or if reclaim_on_free == 1 and the pages is not too full if (heap != NULL && heap->allow_page_reclaim) {
_mi_arena_memid_is_suitable(page->memid,heap->exclusive_arena) // don't reclaim across unsuitable arena's; todo: inline arena_is_suitable (?) if (heap == page->heap || // only reclaim if we were the originating heap,
(reclaim_on_free == 1 && // OR if the reclaim option across heaps is enabled
!mi_page_is_used_at_frac(page, 8) && // and the page is not too full
_mi_arena_memid_is_suitable(page->memid, heap->exclusive_arena)) // and the memory is suitable
) )
{ {
// first remove it from the abandoned pages in the arena -- this waits for any readers to finish // first remove it from the abandoned pages in the arena -- this waits for any readers to finish
@ -248,6 +247,7 @@ static void mi_decl_noinline mi_free_try_collect_mt(mi_page_t* page, mi_block_t*
return; return;
} }
} }
}
// 3. if the page is unmapped, try to reabandon so it can possibly be mapped and found for allocations // 3. if the page is unmapped, try to reabandon so it can possibly be mapped and found for allocations
if (!mi_page_is_used_at_frac(page, 8) && // only reabandon if a full page starts to have enough blocks available to prevent immediate re-abandon of a full page if (!mi_page_is_used_at_frac(page, 8) && // only reabandon if a full page starts to have enough blocks available to prevent immediate re-abandon of a full page