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fix over-eager page reset in segment reclamation

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This commit is contained in:
daan 2020-01-25 13:43:56 -08:00
parent 4faf412f53
commit 394b796ea0
1 changed files with 8 additions and 15 deletions
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23
src/segment.c
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@ -1019,26 +1019,18 @@ void _mi_segment_page_abandon(mi_page_t* page, mi_segments_tld_t* tld) {
----------------------------------------------------------- */
// Possibly clear pages and check if free space is available
static bool mi_segment_pages_collect(mi_segment_t* segment, size_t block_size, mi_segments_tld_t* tld)
static bool mi_segment_check_free(mi_segment_t* segment, size_t block_size)
{
mi_assert_internal(block_size < MI_HUGE_BLOCK_SIZE);
bool has_page = false;
for (size_t i = 0; i < segment->capacity; i++) {
mi_page_t* page = &segment->pages[i];
if (page->segment_in_use) {
mi_assert_internal(!page->is_reset);
mi_assert_internal(page->is_committed);
mi_assert_internal(mi_page_not_in_queue(page, tld));
mi_assert_internal(mi_page_thread_free_flag(page)==MI_NEVER_DELAYED_FREE);
mi_assert_internal(mi_page_heap(page) == NULL);
mi_assert_internal(page->next == NULL);
if (page->segment_in_use) {
// ensure used count is up to date and collect potential concurrent frees
_mi_page_free_collect(page, false);
if (mi_page_all_free(page)) {
// if everything free already, clear the page directly
segment->abandoned--;
_mi_stat_decrease(&tld->stats->pages_abandoned, 1);
mi_segment_page_clear(segment, page, false, tld); // no (delayed) reset allowed (as the segment is still abandoned)
// if everything free already, page can be reused for some block size
// note: don't clear yet as we can only reset it once it is reclaimed
has_page = true;
}
else if (page->xblock_size == block_size && page->used < page->reserved) {
@ -1047,6 +1039,7 @@ static bool mi_segment_pages_collect(mi_segment_t* segment, size_t block_size, m
}
}
else {
// whole empty page
has_page = true;
}
}
@ -1081,7 +1074,6 @@ static mi_segment_t* mi_segment_reclaim(mi_segment_t* segment, mi_heap_t* heap,
// set the heap again and allow delayed free again
mi_page_set_heap(page, heap);
_mi_page_use_delayed_free(page, MI_USE_DELAYED_FREE, true); // override never (after heap is set)
mi_assert_internal(!mi_page_all_free(page));
// TODO: should we not collect again given that we just collected?
_mi_page_free_collect(page, false); // ensure used count is up to date
if (mi_page_all_free(page)) {
@ -1097,7 +1089,8 @@ static mi_segment_t* mi_segment_reclaim(mi_segment_t* segment, mi_heap_t* heap,
}
}
else if (page->is_committed && !page->is_reset) { // not in-use, and not reset yet
mi_pages_reset_add(segment, page, tld);
// note: no not reset as this includes pages that were not touched before
// mi_pages_reset_add(segment, page, tld);
}
}
mi_assert_internal(segment->abandoned == 0);
@ -1146,7 +1139,7 @@ static mi_segment_t* mi_segment_try_reclaim(mi_heap_t* heap, size_t block_size,
int max_tries = 8; // limit the work to bound allocation times
while ((max_tries-- > 0) && ((segment = mi_abandoned_pop()) != NULL)) {
segment->abandoned_visits++;
bool has_page = mi_segment_pages_collect(segment,block_size,tld); // try to free up pages (due to concurrent frees)
bool has_page = mi_segment_check_free(segment,block_size); // try to free up pages (due to concurrent frees)
if (has_page && segment->page_kind == page_kind) {
// found a free page of the right kind, or page of the right block_size with free space
return mi_segment_reclaim(segment, heap, block_size, tld);