[Git][ghc/ghc][wip/hugepages] fixup! rts: Implement support for 2MB hugepages

[Teo Camarasu (@teo)]

Teo Camarasu pushed to branch wip/hugepages at Glasgow Haskell Compiler / GHC


Commits:
4a3fff1b by Teo Camarasu at 2024-08-05T16:11:55+01:00
fixup! rts: Implement support for 2MB hugepages

- - - - -


2 changed files:

- rts/RtsFlags.c
- rts/posix/OSMem.c


Changes:

=====================================
rts/RtsFlags.c
=====================================
@@ -556,8 +556,10 @@ usage_text[] = {
 #endif
 "  -xq        The allocation limit given to a thread after it receives",
 "             an AllocationLimitExceeded exception. (default: 100k)",
+#if defined(HUGEPAGE_FLAGS)
 "  -xH        Try to use hugepages to allocate memory.",
 "",
+#endif
 #if defined(USE_LARGE_ADDRESS_SPACE)
 "  -xr        The size of virtual memory address space reserved by the",
 "             two step allocator (default: 1T)",
@@ -1861,7 +1863,11 @@ error = true;
 
                 case 'H':
                     OPTION_UNSAFE;
+#if defined(HUGEPAGE_FLAGS)
                     RtsFlags.GcFlags.hugepages = true;
+#else
+                    errorBelch("Program not compiled with hugepages support.");
+#endif
                     break;
 
                 default:


=====================================
rts/posix/OSMem.c
=====================================
@@ -60,7 +60,6 @@
 # endif
 #endif
 
-
 #if !defined(darwin_HOST_OS)
 # undef RESERVE_FLAGS
 # if defined(MAP_GUARD)
@@ -74,8 +73,10 @@
 # endif
 #endif
 
+#if defined(HUGEPAGE_FLAGS)
 static int huge_tried = 0;
 static int huge_failed = 0;
+#endif
 
 static void *next_request = 0;
 
@@ -239,8 +240,10 @@ my_mmap (void *addr, W_ size, int operation)
     } else if (operation == MEM_COMMIT) {
         flags = MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE;
 #if defined(HUGEPAGE_FLAGS)
-        if ( RtsFlags.GcFlags.hugepages &&
-            (size & (HUGEPAGE_SIZE - 1)) == 0) {
+        if ( RtsFlags.GcFlags.hugepages ) {
+          // When hugepages are enabled we only free entire hugepages.
+          // This is enforced in `alloc_mega_group`.
+          ASSERT((size & (HUGEPAGE_SIZE - 1)) == 0);
           huge_tried += 1;
           flags |= HUGEPAGE_FLAGS;
         }
@@ -693,7 +696,9 @@ void osDecommitMemory(void *at, W_ size)
         sysErrorBelch("unable to make released memory unaccessible");
 #endif
     if(RtsFlags.GcFlags.hugepages) {
+      // Check that the memory is aligned to a hugepage,
       ASSERT( ((HUGEPAGE_SIZE - 1) & (uintptr_t)at) == 0);
+      // and that it is a multiple of the hugepage size.
       ASSERT( ((HUGEPAGE_SIZE - 1) & size) == 0);
     }
 



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/4a3fff1be01356b69c44175a0b8722101593ccdf

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/4a3fff1be01356b69c44175a0b8722101593ccdf
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