Added 2 HardLimit configs -

GCHeapHardLimit - specifies a hard limit for the GC heap
GCHeapHardLimitPercent - specifies a percentage of the physical memory this process is allowed to use

If both are specified, GCHeapHardLimit is checked first and only when it's not specified
would we check GCHeapHardLimitPercent.

If neither is specified but the process is running inside a container with a memory
limit specified, we will take this as the hard limit:

max (20mb, 75% of the memory limit on the container)

If one of the HardLimit configs is specified, and the process is running inside a container
with a memory limit, the GC heap usage will not exceed the HardLimit but the total memory
is still the memory limit on the container so when we calculate the memory load it's based
off the container memory limit.

An example,

process is running inside a container with 200mb limit
user also specified GCHeapHardLimit as 100mb.

if 50mb out of the 100mb is used for GC, and 100mb is used for other things, the memory load
is (50 + 100)/200 = 75%.

Some notes on these configs -

+ This is only supported on 64-bit.

+ For Server GC the minimum *reserved* segment size is 16mb per heap, this is to avoid the
scenario where the hard limit is small but the process can use many procs and we end up
with tiny segments which doesn't make sense. We then keep track of the committed on the segments
so the total does not exceed the hard limit.

Author: Maoni0

src/ToolBox/SOS/Strike/sos.def

@@ -23,11 +23,9 @@ EXPORTS
     dumpdelegate=DumpDelegate
     DumpDomain
     dumpdomain=DumpDomain
-#ifdef TRACE_GC
     DumpGCLog
     dumpgclog=DumpGCLog
     dlog=DumpGCLog
-#endif     
     DumpGCData
     dumpgcdata=DumpGCData
     dgc=DumpGCData

src/ToolBox/SOS/Strike/strike.cpp

@@ -9419,8 +9419,7 @@ DECLARE_API(DumpLog)
     return Status;
 }
 
-#ifdef TRACE_GC
-
+#ifndef FEATURE_PAL
 DECLARE_API (DumpGCLog)
 {
     INIT_API_NODAC();
@@ -9433,6 +9432,10 @@ DECLARE_API (DumpGCLog)
     }
 
     const char* fileName = "GCLog.txt";
+    int iLogSize = 1024*1024;
+    BYTE* bGCLog = NULL;
+    int iRealLogSize = iLogSize - 1;
+    DWORD dwWritten = 0;
 
     while (isspace (*args))
         args ++;
@@ -9477,8 +9480,7 @@ DECLARE_API (DumpGCLog)
         goto exit;
     }
 
-    int iLogSize = 1024*1024;
-    BYTE* bGCLog = new NOTHROW BYTE[iLogSize];
+    bGCLog = new NOTHROW BYTE[iLogSize];
     if (bGCLog == NULL)
     {
         ReportOOM();
@@ -9491,7 +9493,6 @@ DECLARE_API (DumpGCLog)
         ExtOut("failed to read memory from %08x\n", dwAddr);
     }
 
-    int iRealLogSize = iLogSize - 1;
     while (iRealLogSize >= 0)
     {
         if (bGCLog[iRealLogSize] != '*')
@@ -9502,13 +9503,17 @@ DECLARE_API (DumpGCLog)
         iRealLogSize--;
     }
 
-    DWORD dwWritten = 0;
     WriteFile (hGCLog, bGCLog, iRealLogSize + 1, &dwWritten, NULL);
 
     Status = S_OK;
 
 exit:
 
+    if (bGCLog != NULL)
+    {
+        delete [] bGCLog;
+    }
+
     if (hGCLog != INVALID_HANDLE_VALUE)
     {
         CloseHandle (hGCLog);
@@ -9523,9 +9528,7 @@ DECLARE_API (DumpGCLog)
 
     return Status;
 }
-#endif //TRACE_GC
 
-#ifndef FEATURE_PAL
 DECLARE_API (DumpGCConfigLog)
 {
     INIT_API();

src/gc/env/gcenv.os.h

@@ -341,10 +341,14 @@ class GCToOSInterface
     // Get the physical memory that this process can use.
     // Return:
     //  non zero if it has succeeded, 0 if it has failed
+    //  *is_restricted is set to true if asked and running in restricted.
     // Remarks:
     //  If a process runs with a restricted memory limit, it returns the limit. If there's no limit 
     //  specified, it returns amount of actual physical memory.
-    static uint64_t GetPhysicalMemoryLimit();
+    //
+    // PERF TODO: Requires more work to not treat the restricted case to be special. 
+    // To be removed before 3.0 ships.
+    static uint64_t GetPhysicalMemoryLimit(bool* is_restricted=NULL);
 
     // Get memory status
     // Parameters: