rts: Add support for hugepages

Co-authored-by: Matthew Pickering <matthewtpickering@gmail.com>

4 files changed, 38 insertions, 8 deletions

diff --git a/includes/rts/Constants.h b/includes/rts/Constants.h
index 043099bd1a..6efdd977d8 100644
--- a/includes/rts/Constants.h
+++ b/includes/rts/Constants.h
@@ -170,7 +170,7 @@
 #define BLOCK_SHIFT  12
 
 /* The size of a megablock (2^MBLOCK_SHIFT bytes) */
-#define MBLOCK_SHIFT   20
+#define MBLOCK_SHIFT   21
 
 /* -----------------------------------------------------------------------------
    Bitmap/size fields (used in info tables)
diff --git a/includes/rts/Flags.h b/includes/rts/Flags.h
index 35b45b0940..5b4e29fe3f 100644
--- a/includes/rts/Flags.h
+++ b/includes/rts/Flags.h
@@ -89,6 +89,7 @@ typedef struct _GC_FLAGS {
 
     bool numa;                   /* Use NUMA */
     StgWord numaMask;
+    bool hugepages;              /* Enable hugepages support */
 } GC_FLAGS;
 
 /* See Note [Synchronization of flags and base APIs] */
diff --git a/rts/RtsFlags.c b/rts/RtsFlags.c
index 380ccc3afc..f86191ed57 100644
--- a/rts/RtsFlags.c
+++ b/rts/RtsFlags.c
@@ -182,6 +182,7 @@ void initRtsFlagsDefaults(void)
     RtsFlags.GcFlags.allocLimitGrace    = (100*1024) / BLOCK_SIZE;
     RtsFlags.GcFlags.numa               = false;
     RtsFlags.GcFlags.numaMask           = 1;
+    RtsFlags.GcFlags.hugepages          = false;
     RtsFlags.GcFlags.ringBell           = false;
     RtsFlags.GcFlags.longGCSync         = 0; /* detection turned off */
 
@@ -517,6 +518,7 @@ usage_text[] = {
 #endif
 "  -xq       The allocation limit given to a thread after it receives",
 "            an AllocationLimitExceeded exception. (default: 100k)",
+"  -xH       Use hugepages to allocate huge",
 "",
 "  -Mgrace=<n>",
 "            The amount of allocation after the program receives a",
@@ -1698,13 +1700,18 @@ error = true;
                    */
 
                 case 'q':
-                  OPTION_UNSAFE;
-                  RtsFlags.GcFlags.allocLimitGrace
-                      = decodeSize(rts_argv[arg], 3, BLOCK_SIZE, HS_INT_MAX)
-                          / BLOCK_SIZE;
-                  break;
+                    OPTION_UNSAFE;
+                    RtsFlags.GcFlags.allocLimitGrace
+                        = decodeSize(rts_argv[arg], 3, BLOCK_SIZE, HS_INT_MAX)
+                            / BLOCK_SIZE;
+                    break;
 
-                  default:
+                case 'H':
+                    OPTION_SAFE;
+                    RtsFlags.GcFlags.hugepages = true;
+                    break;
+
+                default:
                     OPTION_SAFE;
                     errorBelch("unknown RTS option: %s",rts_argv[arg]);
                     error = true;
diff --git a/rts/posix/OSMem.c b/rts/posix/OSMem.c
index 30d9981f16..53ea69702d 100644
--- a/rts/posix/OSMem.c
+++ b/rts/posix/OSMem.c
@@ -60,6 +60,11 @@
 # endif
 #endif
 
+#define HUGEPAGE_SIZE (2*1024*1024)
+// This constant is from linux/mman.h
+#define MAP_HUGE_2MB (21 << MAP_HUGE_SHIFT)
+#define HUGEPAGE_FLAGS MAP_HUGETLB
+
 #if !defined(darwin_HOST_OS)
 # undef RESERVE_FLAGS
 # if defined(MAP_GUARD)
@@ -73,6 +78,9 @@
 # endif
 #endif
 
+int huge_tried = 0;
+int huge_failed = 0;
+
 static void *next_request = 0;
 
 void osMemInit(void)
@@ -233,12 +241,24 @@ my_mmap (void *addr, W_ size, int operation)
         errorBelch("my_mmap(,,MEM_RESERVE) not supported on this platform");
 # endif
     } else if (operation == MEM_COMMIT) {
-        flags = MAP_FIXED | MAP_ANON | MAP_PRIVATE;
+        flags = MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE;
+        if ( RtsFlags.GcFlags.hugepages &&
+            (size & (HUGEPAGE_SIZE - 1)) == 0) {
+          huge_tried += 1;
+          flags |= HUGEPAGE_FLAGS;
+        }
     } else {
         flags = MAP_ANON | MAP_PRIVATE;
     }
 
     ret = mmap(addr, size, prot, flags, -1, 0);
+    // If the mmap failed, and we tried with HUGEPAGE_FLAGS
+    // then retry without.
+    if (ret == MAP_FAILED && flags & HUGEPAGE_FLAGS){
+      huge_failed += 1;
+      flags &= ~HUGEPAGE_FLAGS;
+      ret = mmap(addr, size, prot, flags, -1, 0);
+    }
 # if defined(linux_HOST_OS)
     if (ret == MAP_FAILED && errno == EPERM) {
         // Linux may return EPERM if it tried to give us
@@ -472,6 +492,7 @@ void setExecutable (void *p, W_ len, bool exec)
 
 #if defined(USE_LARGE_ADDRESS_SPACE)
 
+
 static void *
 osTryReserveHeapMemory (W_ len, void *hint)
 {
@@ -485,6 +506,7 @@ osTryReserveHeapMemory (W_ len, void *hint)
        and then we discard what we don't need */
 
     base = my_mmap(hint, len + MBLOCK_SIZE, MEM_RESERVE);
+
     if (base == NULL)
         return NULL;