Enable tcache prefetching by default.

Author: guangli-dai

configure.ac

@@ -1434,13 +1434,16 @@ if test "x$enable_experimental_smallocx" = "x1" ; then
 fi
 AC_SUBST([enable_experimental_smallocx])
 
-dnl Do not enable fastpath prefetch by default.
+dnl Enable fastpath prefetch by default.
 AC_ARG_ENABLE([experimental_fp_prefetch],
-  [AS_HELP_STRING([--enable-experimental-fp-prefetch], [Enable experimental fastpath prefetch])],
+  [AS_HELP_STRING([--disable-experimental-fp-prefetch], [Disable experimental fastpath prefetch])],
 [if test "x$enable_experimental_fp_prefetch" = "xno" ; then
-enable_experimental_fp_prefetch="0"
+  enable_experimental_fp_prefetch="0"
 else
-  dnl Check if we have __builtin_prefetch.
+  enable_experimental_fp_prefetch="1"
+fi
+],
+[dnl Check if we have __builtin_prefetch to enable by default.
   JE_CFLAGS_SAVE()
   JE_CFLAGS_ADD([-Werror=implicit-function-declaration])
   JE_COMPILABLE([builtin prefetch], [], [
@@ -1452,12 +1455,9 @@ void foo(void *p) { __builtin_prefetch(p, 1, 3); }
 	   enable_experimental_fp_prefetch="1"
 	else
 	   enable_experimental_fp_prefetch="0"
-	   AC_MSG_ERROR([--enable--experimental-fp-prefetch can only be used when builtin_preftech is available])
 	fi
    JE_CFLAGS_RESTORE()
-fi
-],
-[enable_experimental_fp_prefetch="0"]
+]
 )
 if test "x$enable_experimental_fp_prefetch" = "x1" ; then
   AC_DEFINE([JEMALLOC_EXPERIMENTAL_FASTPATH_PREFETCH], [ ], [ ])

include/jemalloc/internal/jemalloc_internal_defs.h.in

@@ -160,7 +160,8 @@
 /* JEMALLOC_EXPERIMENTAL_SMALLOCX_API enables experimental smallocx API. */
 #undef JEMALLOC_EXPERIMENTAL_SMALLOCX_API
 
-/* JEMALLOC_EXPERIMENTAL_FASTPATH_PREFETCH enables prefetch
+/*
+ * JEMALLOC_EXPERIMENTAL_FASTPATH_PREFETCH enables prefetch
  * on malloc fast path.
  */
 #undef JEMALLOC_EXPERIMENTAL_FASTPATH_PREFETCH