Add methods to enable configuration of ResourceConstraints based on limits derived at runtime.

src/platform-posix.cc

Index: src/platform-posix.cc
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index fe27eaf71f437fcc099ffdebb8e24f60c999921f..09142edcb6a1f5fe2a12b0cd85d22c0942ff689d 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -102,6 +102,48 @@ intptr_t OS::MaxVirtualMemory() {
 }
 
 
+uintptr_t OS::TotalPhysicalMemory() {

[Benedikt Meurer, 2013/09/24 13:47:15]

Shouldn't this return an uint64_t? Otherwise this is going to break in 32-bit
mode applications on a 64-bit machine with more than 4 GiB of RAM, right? Did
you actually test this?

[rmcilroy, 2013/09/24 14:39:23]

You're right.  For some reason I thought a uintptr_t would be a uint64_t on
64bit machines.  I did test ia32, but the truncation ended up leaving >2GB so I
didn't notice it was truncated.

Done.  

+#if V8_OS_MACOSX
+  int mib[2];
+  mib[0] = CTL_HW;
+  mib[1] = HW_MEMSIZE;
+  int64_t size = 0;
+  size_t len = sizeof(size);
+  if (sysctl(mib, 2, &size, &len, NULL, 0) != 0) {
+    UNREACHABLE();
+    return 0;
+  }
+  return static_cast<uintptr_t> size;

[Benedikt Meurer, 2013/09/24 13:47:15]

This static_cast is missing parenthesis.

[rmcilroy, 2013/09/24 14:39:23]

Done.

+#elif V8_OS_FREEBSD
+  int pages, page_size;
+  size_t size = sizeof(pages);
+  sysctlbyname("vm.stats.vm.v_page_count", &pages, &size, NULL, 0);
+  sysctlbyname("vm.stats.vm.v_page_size", &page_size, &size, NULL, 0);
+  if (pages == -1 || page_size == -1) {
+    UNREACHABLE();
+    return 0;
+  }
+  return static_cast<uintptr_t>(pages) * page_size;
+#elif V8_OS_CYGWIN
+  MEMORYSTATUS memory_info;
+  memory_info.dwLength = sizeof(memory_info);
+  if (!GlobalMemoryStatus(&memory_info)) {
+    UNREACHABLE();
+    return 0;
+  }
+  return static_cast<uintptr_t>(memory_info.dwTotalPhys);
+#else
+  intptr_t pages = sysconf(_SC_PHYS_PAGES);
+  intptr_t page_size = sysconf(_SC_PAGESIZE);
+  if (pages == -1 || page_size == -1) {
+    UNREACHABLE();
+    return 0;
+  }
+  return static_cast<uintptr_t>(pages) * page_size;
+#endif
+}
+
+
 int OS::ActivationFrameAlignment() {
 #if V8_TARGET_ARCH_ARM
   // On EABI ARM targets this is required for fp correctness in the