Revert "Enable thp(transparent huge pages) for buffer sizes >=2MB (py…

…torch#95963)"

This reverts commit 3bb16a0.

Reverted pytorch#95963 on behalf of https://github.com/izaitsevfb due to Breaks internal android builds: unused function c10_compute_alignment  [-Werror,-Wunused-function]

c10/core/alignment.h

@@ -14,8 +14,4 @@ constexpr size_t gAlignment = 16;
 constexpr size_t gAlignment = 64;
 #endif
 
-constexpr size_t gPagesize = 4096;
-// since the default thp pagesize is 2MB, enable thp only
-// for buffers of size 2MB or larger to avoid memory bloating
-constexpr size_t gAlloc_threshold_thp = 2 * 1024 * 1024;
 } // namespace c10

c10/core/impl/alloc_cpu.cpp

@@ -41,35 +41,6 @@ void memset_junk(void* data, size_t num) {
   }
 }
 
-#ifdef __linux__
-static inline bool is_thp_alloc_enabled() {
-  static bool value = [&] {
-    const char* ptr = std::getenv("THP_MEM_ALLOC_ENABLE");
-    return ptr != nullptr ? std::atoi(ptr) : 0;
-  }();
-  return value;
-}
-
-inline size_t c10_compute_alignment(size_t nbytes) {
-  static const auto pagesize = sysconf(_SC_PAGESIZE);
-  // for kernels that don't provide page size, default it to 4K
-  const size_t thp_alignment = (gPagesize < 0 ? gPagesize : pagesize);
-  return (is_thp_alloc_enabled() ? thp_alignment : gAlignment);
-}
-
-inline bool is_thp_alloc(size_t nbytes) {
-  // enable thp (transparent huge pages) for larger buffers
-  return (is_thp_alloc_enabled() && (nbytes >= gAlloc_threshold_thp));
-}
-#elif !defined(__ANDROID__) && !defined(_MSC_VER)
-constexpr size_t c10_compute_alignment(C10_UNUSED size_t nbytes) {
-  return gAlignment;
-}
-
-constexpr bool is_thp_alloc(C10_UNUSED size_t nbytes) {
-  return false;
-}
-#endif
 } // namespace
 
 void* alloc_cpu(size_t nbytes) {
@@ -100,7 +71,7 @@ void* alloc_cpu(size_t nbytes) {
       nbytes,
       " bytes.");
 #else
-  int err = posix_memalign(&data, c10_compute_alignment(nbytes), nbytes);
+  int err = posix_memalign(&data, gAlignment, nbytes);
   CAFFE_ENFORCE(
       err == 0,
       "DefaultCPUAllocator: can't allocate memory: you tried to allocate ",
@@ -110,16 +81,6 @@ void* alloc_cpu(size_t nbytes) {
       " (",
       strerror(err),
       ")");
-  if (is_thp_alloc(nbytes)) {
-#ifdef __linux__
-    // MADV_HUGEPAGE advise is available only for linux.
-    // general posix compliant systems can check POSIX_MADV_SEQUENTIAL advise.
-    int ret = madvise(data, nbytes, MADV_HUGEPAGE);
-    if (ret != 0) {
-      TORCH_WARN_ONCE("thp madvise for HUGEPAGE failed with ", strerror(errno));
-    }
-#endif
-  }
 #endif
 
   // move data to a thread's NUMA node

c10/core/impl/alloc_cpu.h

@@ -4,11 +4,6 @@
 
 #include <cstddef>
 
-#ifdef __linux__
-#include <sys/mman.h>
-#include <unistd.h>
-#endif
-
 namespace c10 {
 
 C10_API void* alloc_cpu(size_t nbytes);