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add small cache for thread metadata for programs that create/destroy many OS threads

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This commit is contained in:
daan 2022-04-07 20:17:48 -07:00
parent 3c7ce7d3c6
commit 6e5788d076
1 changed files with 71 additions and 15 deletions
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86
src/init.c
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@ -165,6 +165,68 @@ typedef struct mi_thread_data_s {
mi_tld_t tld;
} mi_thread_data_t;
// Thread meta-data is allocated directly from the OS. For
// some programs that do not use thread pools and allocate and
// destroy many OS threads, this may causes too much overhead
// per thread so we maintain a small cache of recently freed metadata.
#define TD_CACHE_SIZE (8)
static _Atomic(mi_thread_data_t*) td_cache[TD_CACHE_SIZE];
static mi_thread_data_t* mi_thread_data_alloc(void) {
// try to find thread metadata in the cache
mi_thread_data_t* td;
for (int i = 0; i < TD_CACHE_SIZE; i++) {
td = mi_atomic_load_ptr_relaxed(mi_thread_data_t*, &td_cache[i]);
if (td != NULL) {
mi_thread_data_t* expected = td;
if (mi_atomic_cas_weak_acq_rel(&td_cache[i], &expected, NULL)) {
return td;
}
}
}
// if that fails, allocate directly from the OS
td = (mi_thread_data_t*)_mi_os_alloc(sizeof(mi_thread_data_t), &_mi_stats_main);
if (td == NULL) {
// if this fails, try once more. (issue #257)
td = (mi_thread_data_t*)_mi_os_alloc(sizeof(mi_thread_data_t), &_mi_stats_main);
if (td == NULL) {
// really out of memory
_mi_error_message(ENOMEM, "unable to allocate thread local heap metadata (%zu bytes)\n", sizeof(mi_thread_data_t));
}
}
return td;
}
static void mi_thread_data_free( mi_thread_data_t* tdfree ) {
// try to add the thread metadata to the cache
for (int i = 0; i < TD_CACHE_SIZE; i++) {
mi_thread_data_t* td = mi_atomic_load_ptr_relaxed(mi_thread_data_t*, &td_cache[i]);
if (td == NULL) {
mi_thread_data_t* expected = NULL;
if (mi_atomic_cas_weak_acq_rel(&td_cache[i], &expected, tdfree)) {
return;
}
}
}
// if that fails, just free it directly
_mi_os_free(tdfree, sizeof(mi_thread_data_t), &_mi_stats_main);
}
static void mi_thread_data_collect(void) {
// free all thread metadata from the cache
for (int i = 0; i < TD_CACHE_SIZE; i++) {
mi_thread_data_t* td = mi_atomic_load_ptr_relaxed(mi_thread_data_t*, &td_cache[i]);
if (td != NULL) {
mi_thread_data_t* expected = td;
if (mi_atomic_cas_weak_acq_rel(&td_cache[i], &expected, NULL)) {
_mi_os_free( td, sizeof(mi_thread_data_t), &_mi_stats_main );
}
}
}
}
// Initialize the thread local default heap, called from `mi_thread_init`
static bool _mi_heap_init(void) {
if (mi_heap_is_initialized(mi_get_default_heap())) return true;
@ -177,16 +239,9 @@ static bool _mi_heap_init(void) {
}
else {
// use `_mi_os_alloc` to allocate directly from the OS
mi_thread_data_t* td = (mi_thread_data_t*)_mi_os_alloc(sizeof(mi_thread_data_t), &_mi_stats_main); // Todo: more efficient allocation?
if (td == NULL) {
// if this fails, try once more. (issue #257)
td = (mi_thread_data_t*)_mi_os_alloc(sizeof(mi_thread_data_t), &_mi_stats_main);
if (td == NULL) {
// really out of memory
_mi_error_message(ENOMEM, "unable to allocate thread local heap metadata (%zu bytes)\n", sizeof(mi_thread_data_t));
return false;
}
}
mi_thread_data_t* td = mi_thread_data_alloc();
if (td == NULL) return false;
// OS allocated so already zero initialized
mi_tld_t* tld = &td->tld;
mi_heap_t* heap = &td->heap;
@ -242,16 +297,17 @@ static bool _mi_heap_done(mi_heap_t* heap) {
// free if not the main thread
if (heap != &_mi_heap_main) {
mi_assert_internal(heap->tld->segments.count == 0 || heap->thread_id != _mi_thread_id());
_mi_os_free(heap, sizeof(mi_thread_data_t), &_mi_stats_main);
mi_thread_data_free((mi_thread_data_t*)heap);
}
#if 0
// never free the main thread even in debug mode; if a dll is linked statically with mimalloc,
// there may still be delete/free calls after the mi_fls_done is called. Issue #207
else {
mi_thread_data_collect(); // free cached thread metadata
#if 0
// never free the main thread even in debug mode; if a dll is linked statically with mimalloc,
// there may still be delete/free calls after the mi_fls_done is called. Issue #207
_mi_heap_destroy_pages(heap);
mi_assert_internal(heap->tld->heap_backing == &_mi_heap_main);
#endif
}
#endif
return false;
}