src: large pages option: FreeBSD support proposal

Enabling on amd64 and as Linux, are 2MB large.
The ELF section linkage script is compatible only with GNU ld.

PR-URL: #28331
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

configure.py

@@ -1039,22 +1039,23 @@ def configure_node(o):
   else:
     o['variables']['node_use_dtrace'] = 'false'
 
-  if options.node_use_large_pages and flavor != 'linux':
+  if options.node_use_large_pages and not flavor in ('linux', 'freebsd'):
     raise Exception(
       'Large pages are supported only on Linux Systems.')
-  if options.node_use_large_pages and flavor == 'linux':
+  if options.node_use_large_pages and flavor in ('linux', 'freebsd'):
     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.')
-    # Example full version string: 2.6.32-696.28.1.el6.x86_64
-    FULL_KERNEL_VERSION=os.uname()[2]
-    KERNEL_VERSION=FULL_KERNEL_VERSION.split('-')[0]
-    if KERNEL_VERSION < "2.6.38":
-      raise Exception(
-        'Large pages need Linux kernel version >= 2.6.38')
+    if flavor == 'linux':
+      # Example full version string: 2.6.32-696.28.1.el6.x86_64
+      FULL_KERNEL_VERSION=os.uname()[2]
+      KERNEL_VERSION=FULL_KERNEL_VERSION.split('-')[0]
+      if KERNEL_VERSION < "2.6.38" and flavor == 'linux':
+        raise Exception(
+          'Large pages need Linux kernel version >= 2.6.38')
   o['variables']['node_use_large_pages'] = b(options.node_use_large_pages)
 
   if options.no_ifaddrs:

node.gyp

@@ -811,7 +811,7 @@
             }],
           ],
         }],
-        [ 'node_use_large_pages=="true" and OS=="linux"', {
+        [ 'node_use_large_pages=="true" and OS in "linux freebsd"', {
           '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

@@ -21,10 +21,16 @@
 // SPDX-License-Identifier: MIT
 
 #include "node_large_page.h"
+#include "util.h"
+#include "uv.h"
 
 #include <fcntl.h>  // _O_RDWR
 #include <sys/types.h>
 #include <sys/mman.h>
+#if defined(__FreeBSD__)
+#include <sys/sysctl.h>
+#include <sys/user.h>
+#endif
 #include <unistd.h>  // readlink
 
 #include <cerrno>   // NOLINT(build/include)
@@ -39,6 +45,7 @@
 #include <fstream>
 #include <iostream>
 #include <sstream>
+#include <vector>
 
 // The functions in this file map the text segment of node into 2M pages.
 // The algorithm is simple
@@ -88,6 +95,7 @@ inline int64_t hugepage_align_down(int64_t addr) {
 // This is also handling the case where the first line is not the binary
 
 static struct text_region FindNodeTextRegion() {
+#if defined(__linux__)
   std::ifstream ifs;
   std::string map_line;
   std::string permission;
@@ -141,9 +149,68 @@ static struct text_region FindNodeTextRegion() {
   }
 
   ifs.close();
+#elif defined(__FreeBSD__)
+  struct text_region nregion;
+  nregion.found_text_region = false;
+
+  std::string exename;
+  {
+    char selfexe[PATH_MAX];
+    size_t count = sizeof(selfexe);
+    if (uv_exepath(selfexe, &count))
+      return nregion;
+
+    exename = std::string(selfexe, count);
+  }
+
+  size_t numpg;
+  int mib[] = {CTL_KERN, KERN_PROC, KERN_PROC_VMMAP, getpid()};
+  const size_t miblen = arraysize(mib);
+  if (sysctl(mib, miblen, nullptr, &numpg, nullptr, 0) == -1) {
+    return nregion;
+  }
+
+  // for struct kinfo_vmentry
+  numpg = numpg * 4 / 3;
+  auto alg = std::vector<char>(numpg);
+
+  if (sysctl(mib, miblen, alg.data(), &numpg, nullptr, 0) == -1) {
+    return nregion;
+  }
+
+  char* start = alg.data();
+  char* end = start + numpg;
+
+  while (start < end) {
+    kinfo_vmentry* entry = reinterpret_cast<kinfo_vmentry*>(start);
+    const size_t cursz = entry->kve_structsize;
+    if (cursz == 0) {
+      break;
+    }
+
+    if (entry->kve_path[0] == '\0') {
+      continue;
+    }
+    bool excmapping = ((entry->kve_protection & KVME_PROT_READ) &&
+     (entry->kve_protection & KVME_PROT_EXEC));
+
+    if (!strcmp(exename.c_str(), entry->kve_path) && excmapping) {
+      size_t size = entry->kve_end - entry->kve_start;
+      nregion.found_text_region = true;
+      nregion.from =
+         reinterpret_cast<char*>(hugepage_align_up(entry->kve_start));
+      nregion.to =
+         reinterpret_cast<char*>(hugepage_align_down(entry->kve_end));
+      nregion.total_hugepages = size / hps;
+      break;
+    }
+    start += cursz;
+  }
+#endif
   return nregion;
 }
 
+#if defined(__linux__)
 static bool IsTransparentHugePagesEnabled() {
   std::ifstream ifs;
 
@@ -171,6 +238,19 @@ static bool IsTransparentHugePagesEnabled() {
   ifs.close();
   return ret_status;
 }
+#elif defined(__FreeBSD__)
+static bool IsSuperPagesEnabled() {
+  // It is enabled by default on amd64
+  unsigned int super_pages = 0;
+  size_t super_pages_length = sizeof(super_pages);
+  if (sysctlbyname("vm.pmap.pg_ps_enabled", &super_pages,
+      &super_pages_length, nullptr, 0) == -1 ||
+      super_pages < 1) {
+    return false;
+  }
+  return true;
+}
+#endif
 
 // Moving the text region to large pages. We need to be very careful.
 // 1: This function itself should not be moved.
@@ -206,6 +286,7 @@ MoveTextRegionToLargePages(const text_region& r) {
 
   memcpy(nmem, r.from, size);
 
+#if defined(__linux__)
 // We already know the original page is r-xp
 // (PROT_READ, PROT_EXEC, MAP_PRIVATE)
 // We want PROT_WRITE because we are writing into it.
@@ -233,6 +314,17 @@ MoveTextRegionToLargePages(const text_region& r) {
 
     return -1;
   }
+#elif defined(__FreeBSD__)
+  tmem = mmap(start, size,
+              PROT_READ | PROT_WRITE | PROT_EXEC,
+              MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED |
+              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);
@@ -266,14 +358,22 @@ int MapStaticCodeToLargePages() {
     return -1;
   }
 
+#if defined(__linux__)
   if (r.from > reinterpret_cast<void*>(&MoveTextRegionToLargePages))
     return MoveTextRegionToLargePages(r);
 
   return -1;
+#elif defined(__FreeBSD__)
+  return MoveTextRegionToLargePages(r);
+#endif
 }
 
 bool IsLargePagesEnabled() {
+#if defined(__linux__)
   return IsTransparentHugePagesEnabled();
+#else
+  return IsSuperPagesEnabled();
+#endif
 }
 
 }  // namespace node