1 files changed, 131 insertions, 0 deletions
diff --git a/xpcom/base/nsMemoryImpl.cpp b/xpcom/base/nsMemoryImpl.cpp
new file mode 100644
index 0000000000..4996d27c7a
--- /dev/null
+++ b/xpcom/base/nsMemoryImpl.cpp
@@ -0,0 +1,131 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 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 "nsMemory.h"
+#include "nsThreadUtils.h"
+
+#include "nsIObserver.h"
+#include "nsIObserverService.h"
+#include "nsIRunnable.h"
+#include "nsISimpleEnumerator.h"
+
+#include "nsCOMPtr.h"
+#include "mozilla/Services.h"
+#include "mozilla/Atomics.h"
+
+#ifdef ANDROID
+#  include <stdio.h>
+
+// Minimum memory threshold for a device to be considered
+// a low memory platform. This value has be in sync with
+// Java's equivalent threshold, defined in HardwareUtils.java
+#  define LOW_MEMORY_THRESHOLD_KB (384 * 1024)
+#endif
+
+static mozilla::Atomic<bool> sIsFlushing;
+static PRIntervalTime sLastFlushTime = 0;
+
+// static
+bool nsMemory::IsLowMemoryPlatform() {
+#ifdef ANDROID
+  static int sLowMemory =
+      -1;  // initialize to unknown, lazily evaluate to 0 or 1
+  if (sLowMemory == -1) {
+    sLowMemory = 0;  // assume "not low memory" in case file operations fail
+
+    // check if MemTotal from /proc/meminfo is less than LOW_MEMORY_THRESHOLD_KB
+    FILE* fd = fopen("/proc/meminfo", "r");
+    if (!fd) {
+      return false;
+    }
+    uint64_t mem = 0;
+    int rv = fscanf(fd, "MemTotal: %" PRIu64 " kB", &mem);
+    if (fclose(fd)) {
+      return false;
+    }
+    if (rv != 1) {
+      return false;
+    }
+    sLowMemory = (mem < LOW_MEMORY_THRESHOLD_KB) ? 1 : 0;
+  }
+  return (sLowMemory == 1);
+#else
+  return false;
+#endif
+}
+
+static void RunFlushers(const char16_t* aReason) {
+  nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
+  if (os) {
+    // Instead of:
+    //  os->NotifyObservers(this, "memory-pressure", aReason);
+    // we are going to do this manually to see who/what is
+    // deallocating.
+
+    nsCOMPtr<nsISimpleEnumerator> e;
+    os->EnumerateObservers("memory-pressure", getter_AddRefs(e));
+
+    if (e) {
+      nsCOMPtr<nsIObserver> observer;
+      bool loop = true;
+
+      while (NS_SUCCEEDED(e->HasMoreElements(&loop)) && loop) {
+        nsCOMPtr<nsISupports> supports;
+        e->GetNext(getter_AddRefs(supports));
+
+        if (!supports) {
+          continue;
+        }
+
+        observer = do_QueryInterface(supports);
+        observer->Observe(observer, "memory-pressure", aReason);
+      }
+    }
+  }
+
+  sIsFlushing = false;
+}
+
+static nsresult FlushMemory(const char16_t* aReason, bool aImmediate) {
+  if (aImmediate) {
+    // They've asked us to run the flusher *immediately*. We've
+    // got to be on the UI main thread for us to be able to do
+    // that...are we?
+    if (!NS_IsMainThread()) {
+      NS_ERROR("can't synchronously flush memory: not on UI thread");
+      return NS_ERROR_FAILURE;
+    }
+  }
+
+  bool lastVal = sIsFlushing.exchange(true);
+  if (lastVal) {
+    return NS_OK;
+  }
+
+  PRIntervalTime now = PR_IntervalNow();
+
+  // Run the flushers immediately if we can; otherwise, proxy to the
+  // UI thread and run 'em asynchronously.
+  nsresult rv = NS_OK;
+  if (aImmediate) {
+    RunFlushers(aReason);
+  } else {
+    // Don't broadcast more than once every 1000ms to avoid being noisy
+    if (PR_IntervalToMicroseconds(now - sLastFlushTime) > 1000) {
+      nsCOMPtr<nsIRunnable> runnable(NS_NewRunnableFunction(
+          "FlushMemory",
+          [reason = aReason]() -> void { RunFlushers(reason); }));
+      NS_DispatchToMainThread(runnable.forget());
+    }
+  }
+
+  sLastFlushTime = now;
+  return rv;
+}
+
+nsresult nsMemory::HeapMinimize(bool aImmediate) {
+  return FlushMemory(u"heap-minimize", aImmediate);
+}