Rewrite ethread library

Large parts of the ethread library have been rewritten. The
ethread library is an Erlang runtime system internal, portable
thread library used by the runtime system itself.

Most notable improvement is a reader optimized rwlock
implementation which dramatically improve the performance of
read-lock/read-unlock operations on multi processor systems by
avoiding ping-ponging of the rwlock cache lines. The reader
optimized rwlock implementation is used by miscellaneous
rwlocks in the runtime system that are known to be read-locked
frequently, and can be enabled on ETS tables by passing the
`{read_concurrency, true}' option upon table creation. See the
documentation of `ets:new/2' for more information.

The ethread library can now also use the libatomic_ops library
for atomic memory accesses. This makes it possible for the
Erlang runtime system to utilize optimized atomic operations
on more platforms than before. Use the
`--with-libatomic_ops=PATH' configure command line argument
when specifying where the libatomic_ops installation is
located. The libatomic_ops library can be downloaded from:
http://www.hpl.hp.com/research/linux/atomic_ops/

The changed API of the ethread library has also caused
modifications in the Erlang runtime system. Preparations for
the to come "delayed deallocation" feature has also been done
since it depends on the ethread library.

Note: When building for x86, the ethread library will now use
instructions that first appeared on the pentium 4 processor. If
you want the runtime system to be compatible with older
processors (back to 486) you need to pass the
`--enable-ethread-pre-pentium4-compatibility' configure command
line argument when configuring the system.

1 files changed, 40 insertions, 21 deletions

diff --git a/erts/configure.in b/erts/configure.in
index 63bf548c89..157163fe0b 100644
--- a/erts/configure.in
+++ b/erts/configure.in
@@ -61,6 +61,9 @@ if test x"${ERL_TOP}/erts" != x"$srcdir"; then
 fi
 erl_top=${ERL_TOP}
 
+# Remove old configuration information
+/bin/rm -f "$ERL_TOP/erts/CONF_INFO"
+
 # echo XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 # echo X
 # echo "X srcdir  = $srcdir"
@@ -277,20 +280,6 @@ AC_ARG_ENABLE(clock-gettime,
     *) clock_gettime_correction=yes ;;
   esac ], clock_gettime_correction=unknown)
 
-AC_ARG_ENABLE(native-ethr-impls,
-[  --enable-native-ethr-impls enable native ethread implementations
-  --disable-native-ethr-impls disable native ethread implementations],
-[ case "$enableval" in
-    no) disable_native_ethr_impls=yes ;;
-    *)  disable_native_ethr_impls=no ;;
-  esac ], disable_native_ethr_impls=no)
-
-dnl Defined in libraries/megaco/configure.in but we need it here
-dnl also in order to show it to the "top user"
-
-AC_ARG_ENABLE(megaco_flex_scanner_lineno,
-[  --disable-megaco-flex-scanner-lineno disable megaco flex scanner lineno])
-
 dnl Magic test for clearcase.
 OTP_RELEASE=
 if test "${ERLANG_COMMERCIAL_BUILD}" != ""; then
@@ -1049,6 +1038,42 @@ if test $ERTS_BUILD_SMP_EMU = yes; then
 	fi
 
 	AC_DEFINE(ERTS_HAVE_SMP_EMU, 1, [Define if the smp emulator is built])
+
+	case "$ethr_have_native_atomics-$ethr_have_native_spinlock" in
+	  yes-*)
+		;;
+
+	  no-yes)
+
+		test -f "$ERL_TOP/erts/CONF_INFO" ||
+		    echo "" > "$ERL_TOP/erts/CONF_INFO"
+		cat >> $ERL_TOP/erts/CONF_INFO <<EOF
+
+                 No native atomic implementation available.
+                 Fallbacks implemented using spinlocks will be
+                 used. Note that the performance of the SMP
+                 runtime system will suffer due to this.
+
+EOF
+		;;
+
+	  no-no)
+
+		test -f "$ERL_TOP/erts/CONF_INFO" ||
+		    echo "" > "$ERL_TOP/erts/CONF_INFO"
+		cat >> "$ERL_TOP/erts/CONF_INFO" <<EOF
+
+                 No native atomic implementation, nor no native
+                 spinlock implementation available. Fallbacks
+                 implemented using mutexes will be used. Note
+                 that the performance of the SMP runtime system
+                 will suffer much due to this.
+
+EOF
+		;;
+
+	esac
+
 	enable_threads=force
 fi
 
@@ -1221,13 +1246,7 @@ fi
 
 AC_SUBST(EMU_LOCK_CHECKING)
 
-ERTS_INTERNAL_X_LIBS=
-
-AC_CHECK_LIB(kstat, kstat_open,
-[AC_DEFINE(HAVE_KSTAT, 1, [Define if you have kstat])
-ERTS_INTERNAL_X_LIBS="$ERTS_INTERNAL_X_LIBS -lkstat"])
-
-AC_SUBST(ERTS_INTERNAL_X_LIBS)
+ERL_INTERNAL_LIBS
 
 dnl THR_LIBS and THR_DEFS are only used by odbc
 THR_LIBS=$ETHR_X_LIBS