GC update from CoreRT (#6487)

https://github.com/dotnet/corert/tree/master/src/Native/gc 35d3eefeb4d14193433a103411526fa869321a82

Author: jkotas

src/gc/env/gcenv.os.h

@@ -240,9 +240,9 @@ class GCToOSInterface
     //  specified, it returns amount of actual physical memory.
     static uint64_t GetPhysicalMemoryLimit();
 
-    // Get global memory status
+    // Get memory status
     // Parameters:
-    //  memory_load - A number between 0 and 100 that specifies the approximate percentage of physical memory 
+    //  memory_load - A number between 0 and 100 that specifies the approximate percentage of physical memory
     //      that is in use (0 indicates no memory use and 100 indicates full memory use).
     //  available_physical - The amount of physical memory currently available, in bytes.
     //  available_page_file - The maximum amount of memory the current process can commit, in bytes.

src/gc/sample/gcenv.windows.cpp

@@ -13,8 +13,6 @@
 #include "gcenv.h"
 #include "gc.h"
 
-static LARGE_INTEGER performanceFrequency;
-
 MethodTable * g_pFreeObjectMethodTable;
 
 int32_t g_TrapReturningThreads;
@@ -23,12 +21,14 @@ bool g_fFinalizerRunOnShutDown;
 
 GCSystemInfo g_SystemInfo;
 
+static LARGE_INTEGER g_performanceFrequency;
+
 // Initialize the interface implementation
 // Return:
 //  true if it has succeeded, false if it has failed
 bool GCToOSInterface::Initialize()
 {
-    if (!::QueryPerformanceFrequency(&performanceFrequency))
+    if (!::QueryPerformanceFrequency(&g_performanceFrequency))
     {
         return false;
     }
@@ -310,9 +310,12 @@ uint64_t GCToOSInterface::GetPhysicalMemoryLimit()
     return memStatus.ullTotalPhys;
 }
 
-// Get global memory status
+// Get memory status
 // Parameters:
-//  ms - pointer to the structure that will be filled in with the memory status
+//  memory_load - A number between 0 and 100 that specifies the approximate percentage of physical memory
+//      that is in use (0 indicates no memory use and 100 indicates full memory use).
+//  available_physical - The amount of physical memory currently available, in bytes.
+//  available_page_file - The maximum amount of memory the current process can commit, in bytes.
 void GCToOSInterface::GetMemoryStatus(uint32_t* memory_load, uint64_t* available_physical, uint64_t* available_page_file)
 {
     MEMORYSTATUSEX memStatus;
@@ -356,14 +359,7 @@ int64_t GCToOSInterface::QueryPerformanceCounter()
 //  The counter frequency
 int64_t GCToOSInterface::QueryPerformanceFrequency()
 {
-    LARGE_INTEGER frequency;
-    if (!::QueryPerformanceFrequency(&frequency))
-    {
-        _ASSERTE(!"Fatal Error - cannot query performance counter.");
-        abort();
-    }
-
-    return frequency.QuadPart;
+    return g_performanceFrequency.QuadPart;
 }
 
 // Get a time stamp with a low precision

src/vm/gcenv.os.cpp

@@ -534,9 +534,14 @@ uint64_t GCToOSInterface::GetPhysicalMemoryLimit()
     return memStatus.ullTotalPhys;
 }
 
-// Get global memory status
+// Get memory status
 // Parameters:
-//  ms - pointer to the structure that will be filled in with the memory status
+//  memory_load - A number between 0 and 100 that specifies the approximate percentage of physical memory
+//      that is in use (0 indicates no memory use and 100 indicates full memory use).
+//  available_physical - The amount of physical memory currently available, in bytes.
+//  available_page_file - The maximum amount of memory the current process can commit, in bytes.
+// Remarks:
+//  Any parameter can be null.
 void GCToOSInterface::GetMemoryStatus(uint32_t* memory_load, uint64_t* available_physical, uint64_t* available_page_file)
 {
     LIMITED_METHOD_CONTRACT;