remove anon mmap allocation flag `MAP_HUGETLB`

util/arena.cc

@@ -83,8 +83,14 @@ char* Arena::AllocateAligned(size_t bytes, size_t huge_page_tlb_size,
     size_t reserved_size =
         ((bytes - 1U) / huge_page_tlb_size + 1U) * huge_page_tlb_size;
     assert(reserved_size >= bytes);
+
     void* addr = mmap(nullptr, reserved_size, (PROT_READ | PROT_WRITE),
-                      (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB), 0, 0);
+                      (MAP_PRIVATE | MAP_ANONYMOUS), 0, 0);
+
+    // only supported in kernel's 2.6.34 and above
+    // void* addr = mmap(nullptr, reserved_size, (PROT_READ | PROT_WRITE),
+    //                   (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB), 0, 0);
+
     if (addr == MAP_FAILED) {
       Warn(logger, "AllocateAligned fail to allocate huge TLB pages: %s",
            strerror(errno));