Hook up the link pool in the GN build.

build/toolchain/get_concurrent_links.py

Index: build/toolchain/get_concurrent_links.py
diff --git a/build/toolchain/get_concurrent_links.py b/build/toolchain/get_concurrent_links.py
new file mode 100644
index 0000000000000000000000000000000000000000..629d67d5030662c94bf3ea89cb4915f8e0d47ebe
--- /dev/null
+++ b/build/toolchain/get_concurrent_links.py
@@ -0,0 +1,64 @@
+# Copyright 2014 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.
+
+# This script computs the number of concurrent links we want to run in the build
+# as a function of machine spec. It's based on GetDefaultConcurrentLinks in GYP.
+
+import os
+import re
+import sys
+
+def GetDefaultConcurrentLinks():
+  # Inherit the legacy environment variable for people that have set it in GYP.
+  pool_size = int(os.getenv('GYP_LINK_CONCURRENCY', 0))
+  if pool_size:
+    return pool_size
+
+  if sys.platform in ('win32', 'cygwin'):
+    import ctypes
+
+    class MEMORYSTATUSEX(ctypes.Structure):
+      _fields_ = [
+        ("dwLength", ctypes.c_ulong),
+        ("dwMemoryLoad", ctypes.c_ulong),
+        ("ullTotalPhys", ctypes.c_ulonglong),
+        ("ullAvailPhys", ctypes.c_ulonglong),
+        ("ullTotalPageFile", ctypes.c_ulonglong),
+        ("ullAvailPageFile", ctypes.c_ulonglong),
+        ("ullTotalVirtual", ctypes.c_ulonglong),
+        ("ullAvailVirtual", ctypes.c_ulonglong),
+        ("sullAvailExtendedVirtual", ctypes.c_ulonglong),
+      ]
+
+    stat = MEMORYSTATUSEX()
+    stat.dwLength = ctypes.sizeof(stat)
+    ctypes.windll.kernel32.GlobalMemoryStatusEx(ctypes.byref(stat))
+
+    mem_limit = max(1, stat.ullTotalPhys / (4 * (2 ** 30)))  # total / 4GB
+    hard_cap = max(1, int(os.getenv('GYP_LINK_CONCURRENCY_MAX', 2**32)))
+    return min(mem_limit, hard_cap)
+  elif sys.platform.startswith('linux'):
+    if os.path.exists("/proc/meminfo"):
+      with open("/proc/meminfo") as meminfo:
+        memtotal_re = re.compile(r'^MemTotal:\s*(\d*)\s*kB')
+        for line in meminfo:
+          match = memtotal_re.match(line)
+          if not match:
+            continue
+          # Allow 8Gb per link on Linux because Gold is quite memory hungry
+          return max(1, int(match.group(1)) / (8 * (2 ** 20)))
+    return 1
+  elif sys.platform == 'darwin':
+    try:
+      avail_bytes = int(subprocess.check_output(['sysctl', '-n', 'hw.memsize']))
+      # A static library debug build of Chromium's unit_tests takes ~2.7GB, so
+      # 4GB per ld process allows for some more bloat.
+      return max(1, avail_bytes / (4 * (2 ** 30)))  # total / 4GB
+    except:
+      return 1
+  else:
+    # TODO(scottmg): Implement this for other platforms.
+    return 1
+
+print GetDefaultConcurrentLinks()