Add a tool for clearing the system cache for a directory.

tools/perf/clear_system_cache/clear_system_cache.cc

Index: tools/perf/clear_system_cache/clear_system_cache.cc
diff --git a/tools/perf/clear_system_cache/clear_system_cache.cc b/tools/perf/clear_system_cache/clear_system_cache.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f32ca44c5d5264f16545a2dac2923c023da1cc5a
--- /dev/null
+++ b/tools/perf/clear_system_cache/clear_system_cache.cc
@@ -0,0 +1,55 @@
+// Copyright (c) 2013 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.
+
+// A utility to clear the operating system's cache for a file or directory.
+//
+// USAGE: clear_system_cache [--recurse] <files or directories>
+
+#include <stdio.h>
+
+#include "base/basictypes.h"
+#include "base/command_line.h"
+#include "base/file_util.h"
+#include "base/files/file_enumerator.h"
+#include "base/files/file_path.h"
+#include "base/logging.h"
+#include "base/test/test_file_util.h"
+
+void ClearCacheForFile(const base::FilePath& path) {
+  VLOG(1) << "Clearing " << path.MaybeAsASCII();
+  file_util::EvictFileFromSystemCache(path);
+}
+
+int main(int argc, const char* argv[]) {
+  CommandLine::Init(argc, argv);
+  const CommandLine& parsed_command_line = *CommandLine::ForCurrentProcess();
+  bool should_recurse = parsed_command_line.HasSwitch("recurse");
+  const CommandLine::StringVector& args = parsed_command_line.GetArgs();
+
+  if (args.size() < 1) {
+    printf("USAGE: %s [--recurse] <files or directories>\n", argv[0]);
+    return 1;
+  }
+
+  for (size_t i = 0; i < args.size(); ++i) {
+    base::FilePath path(args[i]);
+    if (!base::PathExists(path)) {
+      LOG(ERROR) << "Couldn't find " << path.MaybeAsASCII();
+      continue;

[tonyg, 2013/07/25 21:30:42]

Just a thought, but should we make this fatal and return 1 instead of
continuing. I'm wondering whether a perf test could try to clear the cache for a
file that got moved and silently fail with this error.

[James Simonsen, 2013/07/26 02:14:00]

Done.

+    }
+
+    if (base::DirectoryExists(path)) {
+      base::FileEnumerator enumerator(path, should_recurse,
+                                      base::FileEnumerator::FILES);
+      for (base::FilePath next = enumerator.Next(); !next.empty();
+           next = enumerator.Next()) {
+        ClearCacheForFile(next);
+      }
+    } else {
+      ClearCacheForFile(path);
+    }
+  }
+
+  return 0;
+}