src: add large page support for macOS

Proposal to bring the support for this platform.
We assume the pse36 cpu flag is present for 2MB
large page support present in recent years
in mac line (not to be backported to 10.x anyway).
Recommended better for mac production servers rather
than casual mac books.

PR-URL: #28977
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

configure.py

@@ -1035,16 +1035,18 @@ def configure_node(o):
   else:
     o['variables']['node_use_dtrace'] = 'false'
 
-  if options.node_use_large_pages and not flavor in ('linux', 'freebsd'):
+  if options.node_use_large_pages and not flavor in ('linux', 'freebsd', 'mac'):
     raise Exception(
-      'Large pages are supported only on Linux Systems.')
-  if options.node_use_large_pages and flavor in ('linux', 'freebsd'):
+      'Large pages are supported only on Linux, FreeBSD and MacOS Systems.')
+  if options.node_use_large_pages and flavor in ('linux', 'freebsd', 'mac'):
     if options.shared or options.enable_static:
       raise Exception(
         'Large pages are supported only while creating node executable.')
     if target_arch!="x64":
       raise Exception(
         'Large pages are supported only x64 platform.')
+    if flavor == 'mac':
+      info('macOS server with 32GB or more is recommended')
     if flavor == 'linux':
       # Example full version string: 2.6.32-696.28.1.el6.x86_64
       FULL_KERNEL_VERSION=os.uname()[2]

node.gyp

@@ -817,7 +817,7 @@
             }],
           ],
         }],
-        [ 'node_use_large_pages=="true" and OS in "linux freebsd"', {
+        [ 'node_use_large_pages=="true" and OS in "linux freebsd mac"', {
           'defines': [ 'NODE_ENABLE_LARGE_CODE_PAGES=1' ],
           # The current implementation of Large Pages is under Linux.
           # Other implementations are possible but not currently supported.

src/large_pages/node_large_page.cc

@@ -30,6 +30,8 @@
 #if defined(__FreeBSD__)
 #include <sys/sysctl.h>
 #include <sys/user.h>
+#elif defined(__APPLE__)
+#include <mach/vm_map.h>
 #endif
 #include <unistd.h>  // readlink
 
@@ -212,6 +214,42 @@ static struct text_region FindNodeTextRegion() {
     }
     start += cursz;
   }
+#elif defined(__APPLE__)
+  struct text_region nregion;
+  nregion.found_text_region = false;
+  struct vm_region_submap_info_64 map;
+  mach_msg_type_number_t count = VM_REGION_SUBMAP_INFO_COUNT_64;
+  vm_address_t addr = 0UL;
+  vm_size_t size = 0;
+  natural_t depth = 1;
+
+  while (true) {
+    if (vm_region_recurse_64(mach_task_self(), &addr, &size, &depth,
+                             reinterpret_cast<vm_region_info_64_t>(&map),
+                             &count) != KERN_SUCCESS) {
+      break;
+    }
+
+    if (map.is_submap) {
+      depth++;
+    } else {
+      char* start = reinterpret_cast<char*>(hugepage_align_up(addr));
+      char* end = reinterpret_cast<char*>(hugepage_align_down(addr+size));
+      size_t esize = end - start;
+
+      if (end > start && (map.protection & VM_PROT_READ) != 0 &&
+          (map.protection & VM_PROT_EXECUTE) != 0) {
+        nregion.found_text_region = true;
+        nregion.from = start;
+        nregion.to = end;
+        nregion.total_hugepages = esize / hps;
+        break;
+      }
+
+      addr += size;
+      size = 0;
+    }
+  }
 #endif
   return nregion;
 }
@@ -267,11 +305,15 @@ static bool IsSuperPagesEnabled() {
 // 2: This function should not call any function(s) that might be moved.
 // a. map a new area and copy the original code there
 // b. mmap using the start address with MAP_FIXED so we get exactly
-//    the same virtual address
+//    the same virtual address (except on macOS).
 // c. madvise with MADV_HUGE_PAGE
 // d. If successful copy the code there and unmap the original region
 int
+#if !defined(__APPLE__)
 __attribute__((__section__(".lpstub")))
+#else
+__attribute__((__section__("__TEXT,__lpstub")))
+#endif
 __attribute__((__aligned__(hps)))
 __attribute__((__noinline__))
 MoveTextRegionToLargePages(const text_region& r) {
@@ -289,6 +331,9 @@ MoveTextRegionToLargePages(const text_region& r) {
     PrintSystemError(errno);
     return -1;
   }
+  OnScopeLeave munmap_on_return([nmem, size]() {
+    if (-1 == munmap(nmem, size)) PrintSystemError(errno);
+  });
 
   memcpy(nmem, r.from, size);
 
@@ -302,7 +347,6 @@ MoveTextRegionToLargePages(const text_region& r) {
               MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1 , 0);
   if (tmem == MAP_FAILED) {
     PrintSystemError(errno);
-    munmap(nmem, size);
     return -1;
   }
 
@@ -313,11 +357,6 @@ MoveTextRegionToLargePages(const text_region& r) {
     if (ret == -1) {
       PrintSystemError(errno);
     }
-    ret = munmap(nmem, size);
-    if (ret == -1) {
-      PrintSystemError(errno);
-    }
-
     return -1;
   }
 #elif defined(__FreeBSD__)
@@ -327,32 +366,46 @@ MoveTextRegionToLargePages(const text_region& r) {
               MAP_ALIGNED_SUPER, -1 , 0);
   if (tmem == MAP_FAILED) {
     PrintSystemError(errno);
-    munmap(nmem, size);
     return -1;
   }
-#endif
-
-  memcpy(start, nmem, size);
-  ret = mprotect(start, size, PROT_READ | PROT_EXEC);
+#elif defined(__APPLE__)
+  // There is not enough room to reserve the mapping close
+  // to the region address so we content to give a hint
+  // without forcing the new address being closed to.
+  // We explicitally gives all permission since we plan
+  // to write into it.
+  tmem = mmap(start, size,
+              PROT_READ | PROT_WRITE | PROT_EXEC,
+              MAP_PRIVATE | MAP_ANONYMOUS,
+              VM_FLAGS_SUPERPAGE_SIZE_2MB, 0);
+  if (tmem == MAP_FAILED) {
+    PrintSystemError(errno);
+    return -1;
+  }
+  memcpy(tmem, nmem, size);
+  ret = mprotect(start, size, PROT_READ | PROT_WRITE | PROT_EXEC);
   if (ret == -1) {
     PrintSystemError(errno);
     ret = munmap(tmem, size);
     if (ret == -1) {
       PrintSystemError(errno);
     }
-    ret = munmap(nmem, size);
-    if (ret == -1) {
-      PrintSystemError(errno);
-    }
     return -1;
   }
+  memcpy(start, tmem, size);
+#else
+  memcpy(start, nmem, size);
+#endif
 
-  // Release the old/temporary mapped region
-  ret = munmap(nmem, size);
+  ret = mprotect(start, size, PROT_READ | PROT_EXEC);
   if (ret == -1) {
     PrintSystemError(errno);
+    ret = munmap(tmem, size);
+    if (ret == -1) {
+      PrintSystemError(errno);
+    }
+    return -1;
   }
-
   return ret;
 }
 
@@ -369,16 +422,19 @@ int MapStaticCodeToLargePages() {
     return MoveTextRegionToLargePages(r);
 
   return -1;
-#elif defined(__FreeBSD__)
+#elif defined(__FreeBSD__) || defined(__APPLE__)
   return MoveTextRegionToLargePages(r);
 #endif
 }
 
 bool IsLargePagesEnabled() {
 #if defined(__linux__)
   return IsTransparentHugePagesEnabled();
-#else
+#elif defined(__FreeBSD__)
   return IsSuperPagesEnabled();
+#elif defined(__APPLE__)
+  // pse-36 flag is present in recent mac x64 products.
+  return true;
 #endif
 }