Prefetch the native library from native code by parsing /proc/pid/maps.

base/android/library_loader/library_prefetcher.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ANDROID_LIBRARY_LOADER_LIBRARY_PREFETCHER_H_
+#define BASE_ANDROID_LIBRARY_LOADER_LIBRARY_PREFETCHER_H_
+
+#include <jni.h>
+
+#include <sys/types.h>
+#include <string>
+
+#include "base/files/file_util.h"
+#include "base/gtest_prod_util.h"
+#include "base/macros.h"
+#include "base/strings/string_split.h"
+
+namespace base {
+namespace android {
+
+class NativeLibraryPrefetcher {
+ public:
+  // Finds the ranges matching the native library, forks a low priority
+  // process pre-fetching these ranges and wait()s for it.
+  // Returns false on error.
+  static bool ForkAndPrefetchNativeLibrary();
+
+ private:
+  struct Mapping {
+    uint64_t start;
+    uint64_t end;
+    std::string flags;
+    std::string filename;
+  };
+
+  // Returns true for success.
+  static bool ParseMapping(const std::string& line, Mapping* mapping);
+  // Returns true if the mapping matches native code or data.
+  static bool IsGoodToPrefetch(const Mapping& mapping);
+  // Finds the ranges matching the native library in /proc/self/maps.
+  // Returns true for success.
+  static bool FindRanges(std::vector<std::pair<uint64_t, uint64_t>>* range);
+
+  FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest, TestParseLine32Bits);
+  FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest, TestParseLine64Bits);
+  FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest, TestParseLineNoFile);
+  FRIEND_TEST_ALL_PREFIXES(

[pasko, 2015/03/31 12:01:43]

please to 'git cl format' for this change, it will reduce some formatting churn
later for the new code. Luckily library_loader_hooks.cc is already properly
formatted.

[Benoit L, 2015/03/31 14:00:01]

Done.

+      NativeLibraryPrefetcherTest, TestIsGoodToPrefetchNoRange);
+  FRIEND_TEST_ALL_PREFIXES(
+      NativeLibraryPrefetcherTest, TestIsGoodToPrefetchUnreadableRange);
+  FRIEND_TEST_ALL_PREFIXES(
+      NativeLibraryPrefetcherTest, TestIsGoodToPrefetchSkipSharedRange);
+  FRIEND_TEST_ALL_PREFIXES(
+      NativeLibraryPrefetcherTest, TestIsGoodToPrefetchLibchromeRange);
+  FRIEND_TEST_ALL_PREFIXES(
+      NativeLibraryPrefetcherTest, TestIsGoodToPrefetchBaseApkRange);
+};
+
+}  // namespace android
+}  // namespace base
+
+#endif  // BASE_ANDROID_LIBRARY_LOADER_LIBRARY_PREFETCHER_H_