Improve backtracing-related configuration.

Clean up configuration for backtracing when profiling is enabled, and document the configuration logic in INSTALL. Disable libgcc-based backtracing except on x64 (where it is known to work). Add the --disable-prof-gcc option.
2011-03-15 22:23:12 -07:00 · 2011-03-15 22:23:12 -07:00 · 77f350be08
commit 77f350be08
parent b602daa671
4 changed files with 140 additions and 83 deletions
--- a/jemalloc/INSTALL
+++ b/jemalloc/INSTALL
@ -62,18 +62,23 @@ any of the following arguments (not a definitive list) to 'configure':

 --enable-prof
    Enable heap profiling and leak detection functionality.  See the "opt.prof"
-    option documentation for usage details.
+    option documentation for usage details.  When enabled, there are several
+    approaches to backtracing, and the configure script chooses the first one
+    in the following list that appears to function correctly:

--disable-prof-libgcc
-    Disable the use of libgcc's backtracing functionality.  Ordinarily, libgcc's
-    backtracing functionality is superior to the alternatives, but it may fail
-    to capture backtraces on some systems.
+    + libunwind      (requires --enable-prof-libunwind)
+    + libgcc         (unless --disable-prof-libgcc)
+    + gcc intrinsics (unless --disable-prof-gcc)

 --enable-prof-libunwind
    Use the libunwind library (http://www.nongnu.org/libunwind/) for stack
-    backtracing.  libunwind is quite slow, but it tends to work across a wider
-    variety of system configurations than the default backtracing code, which is
-    based on libgcc functionality or gcc intrinsics.
+    backtracing.
+
+--disable-prof-libgcc
+    Disable the use of libgcc's backtracing functionality.
+
+--disable-prof-gcc
+    Disable the use of gcc intrinsics for backtracing.

 --with-static-libunwind=<libunwind.a>
    Statically link against the specified libunwind.a rather than dynamically
--- a/jemalloc/configure.ac
+++ b/jemalloc/configure.ac
@ -404,17 +404,12 @@ fi
 ],
 [enable_prof="0"]
 )
-AC_ARG_ENABLE([prof-libgcc],
-  [AS_HELP_STRING([--disable-prof-libgcc],
-  [Do not use libgcc for backtracing])],
-[if test "x$enable_prof_libgcc" = "xno" ; then
-  enable_prof_libgcc="0"
+if test "x$enable_prof" = "x1" ; then
+  backtrace_method=""
 else
-  enable_prof_libgcc="1"
+  backtrace_method="N/A"
 fi
-],
-[enable_prof_libgcc="1"]
-)
+
 AC_ARG_ENABLE([prof-libunwind],
  [AS_HELP_STRING([--enable-prof-libunwind], [Use libunwind for backtracing])],
 [if test "x$enable_prof_libunwind" = "xno" ; then
@ -438,39 +433,90 @@ else
 fi,
  LUNWIND="-lunwind"
 )
+if test "x$backtrace_method" = "x" -a "x$enable_prof_libunwind" = "x1" ; then
+  AC_CHECK_HEADERS([libunwind.h], , [enable_prof_libunwind="0"])
+  if test "x$LUNWIND" = "x-lunwind" ; then
+    AC_CHECK_LIB([unwind], [backtrace], [LIBS="$LIBS $LUNWIND"],
+                 [enable_prof_libunwind="0"])
+  else
+    LIBS="$LIBS $LUNWIND"
+  fi
+  if test "x${enable_prof_libunwind}" = "x1" ; then
+    backtrace_method="libunwind"
+    AC_DEFINE([JEMALLOC_PROF_LIBUNWIND], [ ])
+  fi
+fi
+
+AC_ARG_ENABLE([prof-libgcc],
+  [AS_HELP_STRING([--disable-prof-libgcc],
+  [Do not use libgcc for backtracing])],
+[if test "x$enable_prof_libgcc" = "xno" ; then
+  enable_prof_libgcc="0"
+else
+  enable_prof_libgcc="1"
+fi
+],
+[enable_prof_libgcc="1"]
+)
+if test "x$backtrace_method" = "x" -a "x$enable_prof_libgcc" = "x1" \
+     -a "x$GCC" = "xyes" ; then
+  AC_CHECK_HEADERS([unwind.h], , [enable_prof_libgcc="0"])
+  AC_CHECK_LIB([gcc], [_Unwind_Backtrace], [LIBS="$LIBS -lgcc"], [enable_prof_libgcc="0"])
+  dnl The following is conservative, in that it only has entries for CPUs on
+  dnl which jemalloc has been tested.
+  AC_MSG_CHECKING([libgcc-based backtracing reliability on ${host_cpu}])
+  case "${host_cpu}" in
+    i[[3456]]86)
+      AC_MSG_RESULT([unreliable])
+      enable_prof_libgcc="0";
+      ;;
+    x86_64)
+      AC_MSG_RESULT([reliable])
+      ;;
+    *)
+      AC_MSG_RESULT([unreliable])
+      enable_prof_libgcc="0";
+      ;;
+  esac
+  if test "x${enable_prof_libgcc}" = "x1" ; then
+    backtrace_method="libgcc"
+    AC_DEFINE([JEMALLOC_PROF_LIBGCC], [ ])
+  fi
+else
+  enable_prof_libgcc="0"
+fi
+
+AC_ARG_ENABLE([prof-gcc],
+  [AS_HELP_STRING([--disable-prof-gcc],
+  [Do not use gcc intrinsics for backtracing])],
+[if test "x$enable_prof_gcc" = "xno" ; then
+  enable_prof_gcc="0"
+else
+  enable_prof_gcc="1"
+fi
+],
+[enable_prof_gcc="1"]
+)
+if test "x$backtrace_method" = "x" -a "x$enable_prof_gcc" = "x1" \
+     -a "x$GCC" = "xyes" ; then
+  backtrace_method="gcc intrinsics"
+  AC_DEFINE([JEMALLOC_PROF_GCC], [ ])
+else
+  enable_prof_gcc="0"
+fi
+
+if test "x$backtrace_method" = "x" ; then
+  backtrace_method="none (disabling profiling)"
+  enable_prof="0"
+fi
+AC_MSG_CHECKING([configured backtracing method])
+AC_MSG_RESULT([$backtrace_method])
 if test "x$enable_prof" = "x1" ; then
  LIBS="$LIBS -lm"
  AC_DEFINE([JEMALLOC_PROF], [ ])
-  if test "x$enable_prof_libunwind" = "x1" ; then
-    AC_CHECK_HEADERS([libunwind.h], , [enable_prof_libunwind="0"])
-    if test "x$LUNWIND" = "x-lunwind" ; then
-      AC_CHECK_LIB([unwind], [backtrace], [LIBS="$LIBS $LUNWIND"],
-                   [enable_prof_libunwind="0"])
-    else
-      LIBS="$LIBS $LUNWIND"
-    fi
-    if test "x${enable_prof_libunwind}" = "x1" ; then
-      AC_DEFINE([JEMALLOC_PROF_LIBUNWIND], [ ])
-    fi
-  fi
 fi
 AC_SUBST([enable_prof])

-dnl If libunwind isn't enabled, try to use libgcc rather than gcc intrinsics
-dnl for backtracing.
-if test "x$enable_prof" = "x1" -a "x$enable_prof_libgcc" = "x1" ; then
-  if test "x$enable_prof_libunwind" = "x0" -a "x$GCC" = "xyes" ; then
-    enable_prof_libgcc="1"
-    AC_CHECK_HEADERS([unwind.h], , [enable_prof_libgcc="0"])
-    AC_CHECK_LIB([gcc], [_Unwind_Backtrace], [LIBS="$LIBS -lgcc"], [enable_prof_libgcc="0"])
-    if test "x${enable_prof_libgcc}" = "x1" ; then
-      AC_DEFINE([JEMALLOC_PROF_LIBGCC], [ ])
-    fi
-  else
-    enable_prof_libgcc="0"
-  fi
-fi
-
 dnl Enable tiny allocations by default.
 AC_ARG_ENABLE([tiny],
  [AS_HELP_STRING([--disable-tiny], [Disable tiny (sub-quantum) allocations])],
@ -810,8 +856,9 @@ AC_MSG_RESULT([cc-silence         : ${enable_cc_silence}])
 AC_MSG_RESULT([debug              : ${enable_debug}])
 AC_MSG_RESULT([stats              : ${enable_stats}])
 AC_MSG_RESULT([prof               : ${enable_prof}])
-AC_MSG_RESULT([prof-libgcc        : ${enable_prof_libgcc}])
 AC_MSG_RESULT([prof-libunwind     : ${enable_prof_libunwind}])
+AC_MSG_RESULT([prof-libgcc        : ${enable_prof_libgcc}])
+AC_MSG_RESULT([prof-gcc           : ${enable_prof_gcc}])
 AC_MSG_RESULT([tiny               : ${enable_tiny}])
 AC_MSG_RESULT([tcache             : ${enable_tcache}])
 AC_MSG_RESULT([fill               : ${enable_fill}])
--- a/jemalloc/include/jemalloc/jemalloc_defs.h.in
+++ b/jemalloc/include/jemalloc/jemalloc_defs.h.in
@ -53,6 +53,9 @@
 /* Use libgcc for profile backtracing if defined. */
 #undef JEMALLOC_PROF_LIBGCC

+/* Use gcc intrinsics for profile backtracing if defined. */
+#undef JEMALLOC_PROF_GCC
+
 /*
 * JEMALLOC_TINY enables support for tiny objects, which are smaller than one
 * quantum.
--- a/jemalloc/src/prof.c
+++ b/jemalloc/src/prof.c
@ -3,15 +3,15 @@
 #ifdef JEMALLOC_PROF
 /******************************************************************************/

-#ifdef JEMALLOC_PROF_LIBGCC
-#include <unwind.h>
-#endif
-
 #ifdef JEMALLOC_PROF_LIBUNWIND
 #define	UNW_LOCAL_ONLY
 #include <libunwind.h>
 #endif

+#ifdef JEMALLOC_PROF_LIBGCC
+#include <unwind.h>
+#endif
+
 /******************************************************************************/
 /* Data. */

@ -169,39 +169,7 @@ prof_leave(void)
 		prof_gdump();
 }

-#ifdef JEMALLOC_PROF_LIBGCC
-static _Unwind_Reason_Code
-prof_unwind_init_callback(struct _Unwind_Context *context, void *arg)
-{
-
-	return (_URC_NO_REASON);
-}
-
-static _Unwind_Reason_Code
-prof_unwind_callback(struct _Unwind_Context *context, void *arg)
-{
-	prof_unwind_data_t *data = (prof_unwind_data_t *)arg;
-
-	if (data->nignore > 0)
-		data->nignore--;
-	else {
-		data->bt->vec[data->bt->len] = (void *)_Unwind_GetIP(context);
-		data->bt->len++;
-		if (data->bt->len == data->max)
-			return (_URC_END_OF_STACK);
-	}
-
-	return (_URC_NO_REASON);
-}
-
-void
-prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
-{
-	prof_unwind_data_t data = {bt, nignore, max};
-
-	_Unwind_Backtrace(prof_unwind_callback, &data);
-}
-#elif defined(JEMALLOC_PROF_LIBUNWIND)
+#ifdef JEMALLOC_PROF_LIBUNWIND
 void
 prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
 {
@ -236,7 +204,41 @@ prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
 			break;
 	}
 }
-#else
+#endif
+#ifdef JEMALLOC_PROF_LIBGCC
+static _Unwind_Reason_Code
+prof_unwind_init_callback(struct _Unwind_Context *context, void *arg)
+{
+
+	return (_URC_NO_REASON);
+}
+
+static _Unwind_Reason_Code
+prof_unwind_callback(struct _Unwind_Context *context, void *arg)
+{
+	prof_unwind_data_t *data = (prof_unwind_data_t *)arg;
+
+	if (data->nignore > 0)
+		data->nignore--;
+	else {
+		data->bt->vec[data->bt->len] = (void *)_Unwind_GetIP(context);
+		data->bt->len++;
+		if (data->bt->len == data->max)
+			return (_URC_END_OF_STACK);
+	}
+
+	return (_URC_NO_REASON);
+}
+
+void
+prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
+{
+	prof_unwind_data_t data = {bt, nignore, max};
+
+	_Unwind_Backtrace(prof_unwind_callback, &data);
+}
+#endif
+#ifdef JEMALLOC_PROF_GCC
 void
 prof_backtrace(prof_bt_t *bt, unsigned nignore, unsigned max)
 {