posix: split linux-specific bits out of sys_info_posix

base/sys_info_linux.cc

+// Copyright (c) 2009 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.
+
+#include "base/sys_info.h"
+
+#include "base/file_util.h"
+#include "base/logging.h"
+
+namespace base {
+
+int64 SysInfo::AmountOfPhysicalMemory() {
+  long pages = sysconf(_SC_PHYS_PAGES);
+  long page_size = sysconf(_SC_PAGE_SIZE);
+  if (pages == -1 || page_size == -1) {
+    NOTREACHED();
+    return 0;
+  }
+
+  return static_cast<int64>(pages) * page_size;
+}
+
+// static
+size_t SysInfo::MaxSharedMemorySize() {
+  static size_t limit;
+  static bool limit_valid = false;
+  if (!limit_valid) {
+    std::string contents;
+    file_util::ReadFileToString(FilePath("/proc/sys/kernel/shmmax"), &contents);
+    limit = strtoul(contents.c_str(), NULL, 0);
+    limit_valid = true;
+  }
+  return limit;
+}
+
+}  // namespace base