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--- libmalloc/libmalloc-317.140.5/src/magazine_small.c
+++ libmalloc/libmalloc-792.80.2/src/magazine_small.c
@@ -66,25 +66,6 @@
meta_headers[index] = 0;
}
-static MALLOC_INLINE MALLOC_ALWAYS_INLINE
-mag_index_t
-small_mag_get_thread_index(void)
-{
-#if CONFIG_SMALL_USES_HYPER_SHIFT
- if (os_likely(_os_cpu_number_override == -1)) {
- return _malloc_cpu_number() >> hyper_shift;
- } else {
- return _os_cpu_number_override >> hyper_shift;
- }
-#else // CONFIG_SMALL_USES_HYPER_SHIFT
- if (os_likely(_os_cpu_number_override == -1)) {
- return _malloc_cpu_number();
- } else {
- return _os_cpu_number_override;
- }
-#endif // CONFIG_SMALL_USES_HYPER_SHIFT
-}
-
#pragma mark in-place free list
static MALLOC_INLINE void
@@ -833,8 +814,8 @@
OSAtomicIncrement32Barrier(&(REGION_TRAILER_FOR_SMALL_REGION(r)->pinned_to_depot));
SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
for (i = 0; i < advisories; ++i) {
- uintptr_t addr = (advisory[i].pnum << vm_page_quanta_shift) + (uintptr_t)r;
- size_t size = advisory[i].size << vm_page_quanta_shift;
+ uintptr_t addr = (advisory[i].pnum << vm_kernel_page_shift) + (uintptr_t)r;
+ size_t size = advisory[i].size << vm_kernel_page_shift;
mvm_madvise_free(rack, r, addr, addr + size, NULL, rack->debug_flags & MALLOC_DO_SCRIBBLE);
}
@@ -916,11 +897,6 @@
{
magazine_t *depot_ptr = &(rack->magazines[DEPOT_MAGAZINE_INDEX]);
- /* FIXME: Would Uniprocessor benefit from recirc and MADV_FREE? */
- if (rack->num_magazines == 1) { // Uniprocessor, single magazine, so no recirculation necessary
- return 0;
- }
-
#if DEBUG_MALLOC
if (DEPOT_MAGAZINE_INDEX == mag_index) {
malloc_zone_error(rack->debug_flags, true, "small_get_region_from_depot called for magazine index -1\n", NULL, NULL);
@@ -933,22 +909,32 @@
// Appropriate a Depot'd region that can satisfy requested msize.
region_trailer_t *node;
region_t sparse_region;
+ msize_t try_msize = msize;
while (1) {
- sparse_region = small_find_msize_region(rack, depot_ptr, DEPOT_MAGAZINE_INDEX, msize);
+ sparse_region = small_find_msize_region(rack, depot_ptr, DEPOT_MAGAZINE_INDEX, try_msize);
if (NULL == sparse_region) { // Depot empty?
SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
return 0;
}
node = REGION_TRAILER_FOR_SMALL_REGION(sparse_region);
- if (0 >= node->pinned_to_depot) {
+ if (0 == node->pinned_to_depot) {
+ // Found one!
break;
}
- SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
- yield();
- SZONE_MAGAZINE_PTR_LOCK(depot_ptr);
+ // Try the next msize up - maybe the head of its free list will be in
+ // a region we can use. Once we get the region we'll still allocate the
+ // original msize.
+ try_msize++;
+
+ if (try_msize > NUM_SMALL_SLOTS) {
+ // Tried all the msizes but couldn't get a usable region. Let's
+ // give up for now and we'll allocate a new region from the kernel.
+ SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
+ return 0;
+ }
}
// disconnect node from Depot
@@ -959,7 +945,7 @@
// Transfer ownership of the region
MAGAZINE_INDEX_FOR_SMALL_REGION(sparse_region) = mag_index;
- node->pinned_to_depot = 0;
+ MALLOC_ASSERT(node->pinned_to_depot == 0);
// Iterate the region putting its free entries on its new (locked) magazine's free list
size_t bytes_inplay = small_free_reattach_region(rack, small_mag_ptr, sparse_region);
@@ -1031,6 +1017,11 @@
continue;
}
+ if (REGION_TRAILER_FOR_SMALL_REGION(small)->pinned_to_depot > 0) {
+ SZONE_MAGAZINE_PTR_UNLOCK(mag_ptr);
+ continue;
+ }
+
if (small == mag_ptr->mag_last_region && (mag_ptr->mag_bytes_free_at_end || mag_ptr->mag_bytes_free_at_start)) {
small_finalize_region(rack, mag_ptr);
}
@@ -1045,7 +1036,7 @@
SZONE_MAGAZINE_PTR_LOCK(small_depot_ptr);
MAGAZINE_INDEX_FOR_SMALL_REGION(small) = DEPOT_MAGAZINE_INDEX;
- REGION_TRAILER_FOR_SMALL_REGION(small)->pinned_to_depot = 0;
+ MALLOC_ASSERT(REGION_TRAILER_FOR_SMALL_REGION(small)->pinned_to_depot == 0);
size_t bytes_inplay = small_free_reattach_region(rack, small_depot_ptr, small);
@@ -1262,11 +1253,7 @@
region_trailer_t *node = REGION_TRAILER_FOR_SMALL_REGION(region);
size_t bytes_used = node->bytes_used;
- /* FIXME: Would Uniprocessor benefit from recirc and MADV_FREE? */
- if (rack->num_magazines == 1) { // Uniprocessor, single magazine, so no recirculation necessary
- /* NOTHING */
- return TRUE; // Caller must do SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr)
- } else if (DEPOT_MAGAZINE_INDEX != mag_index) {
+ if (DEPOT_MAGAZINE_INDEX != mag_index) {
// Emptiness discriminant
if (small_region_below_recirc_threshold(region)) {
/* Region has crossed threshold from density to sparsity. Mark it "suitable" on the
@@ -2075,7 +2062,7 @@
small_malloc_should_clear(rack_t *rack, msize_t msize, boolean_t cleared_requested)
{
void *ptr;
- mag_index_t mag_index = small_mag_get_thread_index() % rack->num_magazines;
+ mag_index_t mag_index = rack_get_thread_index(rack) % rack->num_magazines;
magazine_t *small_mag_ptr = &(rack->magazines[mag_index]);
MALLOC_TRACE(TRACE_small_malloc, (uintptr_t)rack, SMALL_BYTES_FOR_MSIZE(msize), (uintptr_t)small_mag_ptr, cleared_requested);
@@ -2126,16 +2113,17 @@
// The magazine is exhausted. A new region (heap) must be allocated to satisfy this call to malloc().
// The allocation, an mmap() system call, will be performed outside the magazine spin locks by the first
- // thread that suffers the exhaustion. That thread sets "alloc_underway" and enters a critical section.
- // Threads arriving here later are excluded from the critical section, yield the CPU, and then retry the
- // allocation. After some time the magazine is resupplied, the original thread leaves with its allocation,
- // and retry-ing threads succeed in the code just above.
- if (!small_mag_ptr->alloc_underway) {
+ // thread that suffers the exhaustion. That thread accquires the magazine_alloc_lock, then drops the
+ // magazine lock to allow freeing threads to proceed. Allocating thrads that arrive later are excluded
+ // from the critial section by the alloc lock. When those are unblocked, they succeed in the code above.
+ //
+ // Note that we need to trylock the alloc lock to avoid a deadlock, since we can't block on the alloc
+ // lock while holding the magazine lock
+ if (os_likely(_malloc_lock_trylock(&small_mag_ptr->magazine_alloc_lock))) {
+ // We got the alloc lock, so we are the thread that should allocate a new region
void *fresh_region;
// time to create a new region (do this outside the magazine lock)
- small_mag_ptr->alloc_underway = TRUE;
- OSMemoryBarrier();
SZONE_MAGAZINE_PTR_UNLOCK(small_mag_ptr);
fresh_region = mvm_allocate_pages(SMALL_REGION_SIZE,
SMALL_BLOCKS_ALIGN,
@@ -2147,9 +2135,8 @@
MAGMALLOC_ALLOCREGION(SMALL_SZONE_FROM_RACK(rack), (int)mag_index, fresh_region, SMALL_REGION_SIZE);
if (!fresh_region) { // out of memory!
- small_mag_ptr->alloc_underway = FALSE;
- OSMemoryBarrier();
SZONE_MAGAZINE_PTR_UNLOCK(small_mag_ptr);
+ _malloc_lock_unlock(&small_mag_ptr->magazine_alloc_lock);
return NULL;
}
@@ -2157,14 +2144,20 @@
ptr = small_malloc_from_region_no_lock(rack, small_mag_ptr, mag_index, msize, fresh_region);
// we don't clear because this freshly allocated space is pristine
- small_mag_ptr->alloc_underway = FALSE;
- OSMemoryBarrier();
SZONE_MAGAZINE_PTR_UNLOCK(small_mag_ptr);
+ _malloc_lock_unlock(&small_mag_ptr->magazine_alloc_lock);
CHECK(szone, __PRETTY_FUNCTION__);
return ptr;
} else {
+ // We failed to get the alloc lock, so someone else is allocating.
+ // Drop the magazine lock...
SZONE_MAGAZINE_PTR_UNLOCK(small_mag_ptr);
- yield();
+
+ // Wait for the other thread on the alloc lock
+ _malloc_lock_lock(&small_mag_ptr->magazine_alloc_lock);
+ _malloc_lock_unlock(&small_mag_ptr->magazine_alloc_lock);
+
+ // Reacquire the magazine lock to go around the loop again
SZONE_MAGAZINE_PTR_LOCK(small_mag_ptr);
}
}