1 files changed, 96 insertions, 0 deletions
diff --git a/js/src/gc/MallocedBlockCache.cpp b/js/src/gc/MallocedBlockCache.cpp
new file mode 100644
index 0000000000..627f4d9dcc
--- /dev/null
+++ b/js/src/gc/MallocedBlockCache.cpp
@@ -0,0 +1,96 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sw=2 et tw=80:
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gc/MallocedBlockCache.h"
+#include "mozilla/MemoryChecking.h"
+
+using js::PointerAndUint7;
+using js::gc::MallocedBlockCache;
+
+MallocedBlockCache::~MallocedBlockCache() { clear(); }
+
+// This is the fallback path for MallocedBlockCache::alloc.  Do not call this
+// directly, since it doesn't handle all cases by itself.  See ::alloc for
+// further comments.
+PointerAndUint7 MallocedBlockCache::allocSlow(size_t size) {
+  // We're never expected to handle zero-sized blocks.
+  MOZ_ASSERT(size > 0);
+
+  size = js::RoundUp(size, STEP);
+  size_t i = size / STEP;
+  MOZ_ASSERT(i > 0);
+
+  // Too large to cache; go straight to js_malloc.
+  if (MOZ_UNLIKELY(i >= NUM_LISTS)) {
+    void* p = js_malloc(size);
+    // If p is nullptr, that fact is carried into the PointerAndUint7, and the
+    // caller is expected to check that.
+    return PointerAndUint7(p, OVERSIZE_BLOCK_LIST_ID);
+  }
+
+  // The block is of cacheable size, but we expect the relevant list to be
+  // empty, because ::alloc will have handled the case where it wasn't.
+  MOZ_ASSERT(i >= 1 && i < NUM_LISTS);
+  // Check that i is the right list
+  MOZ_ASSERT(i * STEP == size);
+  MOZ_RELEASE_ASSERT(lists[i].empty());
+
+  // And so we have to hand the request off to js_malloc.
+  void* p = js_malloc(size);
+  if (MOZ_UNLIKELY(!p)) {
+    return PointerAndUint7(nullptr, 0);  // OOM
+  }
+  return PointerAndUint7(p, i);
+}
+
+void MallocedBlockCache::preen(double percentOfBlocksToDiscard) {
+  MOZ_ASSERT(percentOfBlocksToDiscard >= 0.0 &&
+             percentOfBlocksToDiscard <= 100.0);
+  MOZ_ASSERT(lists[OVERSIZE_BLOCK_LIST_ID].empty());
+  for (size_t listID = 1; listID < NUM_LISTS; listID++) {
+    MallocedBlockVector& list = lists[listID];
+    size_t numToFree =
+        size_t(float(list.length()) * (percentOfBlocksToDiscard / 100.0));
+    MOZ_RELEASE_ASSERT(numToFree <= list.length());
+    while (numToFree > 0) {
+      void* block = list.popCopy();
+      MOZ_ASSERT(block);
+      js_free(block);
+      numToFree--;
+    }
+  }
+}
+
+void MallocedBlockCache::clear() {
+  MOZ_ASSERT(lists[OVERSIZE_BLOCK_LIST_ID].empty());
+  for (size_t i = 1; i < NUM_LISTS; i++) {
+    MallocedBlockVector& list = lists[i];
+    for (void*& block : list) {
+      MOZ_ASSERT(block);
+      js_free(block);
+      block = nullptr;  // for safety
+    }
+    list.clear();
+  }
+}
+
+size_t MallocedBlockCache::sizeOfExcludingThis(
+    mozilla::MallocSizeOf mallocSizeOf) const {
+  MOZ_ASSERT(lists[OVERSIZE_BLOCK_LIST_ID].empty());
+  size_t nBytes = 0;
+  for (const MallocedBlockVector& list : lists) {
+    nBytes += list.sizeOfExcludingThis(mallocSizeOf);
+    // The payload size of each block in `list` is the same.  Hence, we could
+    // possibly do better here (measure once and multiply by the length) if we
+    // believe that the metadata size for each block is also the same.
+    for (void* block : list) {
+      MOZ_ASSERT(block);
+      nBytes += mallocSizeOf(block);
+    }
+  }
+  return nBytes;
+}