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.

2 files changed, 322 insertions, 0 deletions

diff --git a/erts/include/internal/libatomic_ops/ethr_atomic.h b/erts/include/internal/libatomic_ops/ethr_atomic.h
new file mode 100644
index 0000000000..a6eb43a0bd
--- /dev/null
+++ b/erts/include/internal/libatomic_ops/ethr_atomic.h
@@ -0,0 +1,292 @@
+/*
+ * %CopyrightBegin%
+ *
+ * Copyright Ericsson AB 2010. All Rights Reserved.
+ *
+ * The contents of this file are subject to the Erlang Public License,
+ * Version 1.1, (the "License"); you may not use this file except in
+ * compliance with the License. You should have received a copy of the
+ * Erlang Public License along with this software. If not, it can be
+ * retrieved online at http://www.erlang.org/.
+ *
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * %CopyrightEnd%
+ */
+
+/*
+ * Description: Native atomics ethread support using libatomic_ops
+ * Author: Rickard Green
+ */
+
+#ifndef ETHR_LIBATOMIC_OPS_ATOMIC_H__
+#define ETHR_LIBATOMIC_OPS_ATOMIC_H__
+
+#if !defined(ETHR_HAVE_NATIVE_ATOMICS) && defined(ETHR_HAVE_LIBATOMIC_OPS)
+#define ETHR_HAVE_NATIVE_ATOMICS 1
+
+#if (defined(__i386__) && !defined(ETHR_PRE_PENTIUM4_COMPAT)) \
+    || defined(__x86_64__)
+#define AO_USE_PENTIUM4_INSTRS
+#endif
+
+#include "atomic_ops.h"
+
+/*
+ * libatomic_ops can be downloaded from:
+ *   http://www.hpl.hp.com/research/linux/atomic_ops/
+ *
+ * These operations need to be defined by libatomic_ops;
+ * otherwise, we won't compile:
+ * - AO_nop_full()
+ * - AO_load()
+ * - AO_store()
+ * - AO_compare_and_swap()
+ *
+ * The `AO_t' type also have to be at least as large as
+ * `void *' and `long' types.
+ */
+
+#if ETHR_SIZEOF_AO_T < ETHR_SIZEOF_PTR
+#error The AO_t type is too small
+#endif
+
+typedef struct {
+    volatile AO_t counter;
+} ethr_native_atomic_t;
+
+#define ETHR_MEMORY_BARRIER AO_nop_full()
+#ifdef AO_HAVE_nop_write
+# define ETHR_WRITE_MEMORY_BARRIER AO_nop_write()
+#else
+# define ETHR_WRITE_MEMORY_BARRIER ETHR_MEMORY_BARRIER
+#endif
+#ifdef AO_HAVE_nop_read
+#  define ETHR_READ_MEMORY_BARRIER AO_nop_read()
+#else
+#  define ETHR_READ_MEMORY_BARRIER ETHR_MEMORY_BARRIER
+#endif
+#ifdef AO_NO_DD_ORDERING
+#  define ETHR_READ_DEPEND_MEMORY_BARRIER ETHR_READ_MEMORY_BARRIER
+#else
+#  define ETHR_READ_DEPEND_MEMORY_BARRIER __asm__ __volatile__("":::"memory")
+#endif
+
+#if defined(ETHR_TRY_INLINE_FUNCS) || defined(ETHR_AUX_IMPL__)
+
+static ETHR_INLINE void
+ethr_native_atomic_set(ethr_native_atomic_t *var, long value)
+{
+    AO_store(&var->counter, (AO_t) value);
+}
+
+static ETHR_INLINE void
+ethr_native_atomic_init(ethr_native_atomic_t *var, long value)
+{
+    ethr_native_atomic_set(var, value);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_read(ethr_native_atomic_t *var)
+{
+    return (long) AO_load(&var->counter);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_add_return(ethr_native_atomic_t *var, long incr)
+{
+#ifdef AO_HAVE_fetch_and_add
+    return ((long) AO_fetch_and_add(&var->counter, (AO_t) incr)) + incr;
+#else
+    while (1) {
+	AO_t exp = AO_load(&var->counter);
+	AO_t new = exp + (AO_t) incr;
+	if (AO_compare_and_swap(&var->counter, exp, new))
+	    return (long) new;
+    }
+#endif
+}
+
+static ETHR_INLINE void
+ethr_native_atomic_add(ethr_native_atomic_t *var, long incr)
+{
+    (void) ethr_native_atomic_add_return(var, incr);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_inc_return(ethr_native_atomic_t *var)
+{
+#ifdef AO_HAVE_fetch_and_add1
+    return ((long) AO_fetch_and_add1(&var->counter)) + 1;
+#else
+    return ethr_native_atomic_add_return(var, 1);
+#endif
+}
+
+static ETHR_INLINE void
+ethr_native_atomic_inc(ethr_native_atomic_t *var)
+{
+    (void) ethr_native_atomic_inc_return(var);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_dec_return(ethr_native_atomic_t *var)
+{
+#ifdef AO_HAVE_fetch_and_sub1
+    return ((long) AO_fetch_and_sub1(&var->counter)) - 1;
+#else
+    return ethr_native_atomic_add_return(var, -1);
+#endif
+}
+
+static ETHR_INLINE void
+ethr_native_atomic_dec(ethr_native_atomic_t *var)
+{
+    (void) ethr_native_atomic_dec_return(var);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_and_retold(ethr_native_atomic_t *var, long mask)
+{
+    while (1) {
+	AO_t exp = AO_load(&var->counter);
+	AO_t new = exp & ((AO_t) mask);
+	if (AO_compare_and_swap(&var->counter, exp, new))
+	    return (long) exp;
+    }
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_or_retold(ethr_native_atomic_t *var, long mask)
+{
+    while (1) {
+	AO_t exp = AO_load(&var->counter);
+	AO_t new = exp | ((AO_t) mask);
+	if (AO_compare_and_swap(&var->counter, exp, new))
+	    return (long) exp;
+    }
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_cmpxchg(ethr_native_atomic_t *var, long new, long exp)
+{
+    long act;
+    do {
+	if (AO_compare_and_swap(&var->counter, (AO_t) exp, (AO_t) new))
+	    return exp;
+	act = (long) AO_load(&var->counter);
+    } while (act == exp);
+    return act;
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_xchg(ethr_native_atomic_t *var, long new)
+{
+    while (1) {
+	AO_t exp = AO_load(&var->counter);
+	if (AO_compare_and_swap(&var->counter, exp, (AO_t) new))
+	    return (long) exp;
+    }
+}
+
+/*
+ * Atomic ops with at least specified barriers.
+ */
+
+static ETHR_INLINE long
+ethr_native_atomic_read_acqb(ethr_native_atomic_t *var)
+{
+#ifdef AO_HAVE_load_acquire
+    return (long) AO_load_acquire(&var->counter);
+#else
+    long res = ethr_native_atomic_read(var);
+    ETHR_MEMORY_BARRIER;
+    return res;
+#endif
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_inc_return_acqb(ethr_native_atomic_t *var)
+{
+#ifdef AO_HAVE_fetch_and_add1_acquire
+    return ((long) AO_fetch_and_add1_acquire(&var->counter)) + 1;
+#else
+    long res = ethr_native_atomic_add_return(var, 1);
+    ETHR_MEMORY_BARRIER;
+    return res;
+#endif
+}
+
+static ETHR_INLINE void
+ethr_native_atomic_set_relb(ethr_native_atomic_t *var, long value)
+{
+#ifdef AO_HAVE_store_release
+    AO_store_release(&var->counter, (AO_t) value);
+#else
+    ETHR_MEMORY_BARRIER;
+    ethr_native_atomic_set(var, value);
+#endif
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_dec_return_relb(ethr_native_atomic_t *var)
+{
+#ifdef AO_HAVE_fetch_and_sub1_release
+    return ((long) AO_fetch_and_sub1_release(&var->counter)) - 1;
+#else
+    ETHR_MEMORY_BARRIER;
+    return ethr_native_atomic_dec_return(var);
+#endif
+}
+
+static ETHR_INLINE void
+ethr_native_atomic_dec_relb(ethr_native_atomic_t *var)
+{
+    (void) ethr_native_atomic_dec_return_relb(var);
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_cmpxchg_acqb(ethr_native_atomic_t *var, long new, long exp)
+{
+#ifdef AO_HAVE_compare_and_swap_acquire
+    long act;
+    do {
+	if (AO_compare_and_swap_acquire(&var->counter, (AO_t) exp, (AO_t) new))
+	    return exp;
+	act = (long) AO_load(&var->counter);
+    } while (act == exp);
+    AO_nop_full();
+    return act;
+#else
+    long act = ethr_native_atomic_cmpxchg(var, new, exp);
+    ETHR_MEMORY_BARRIER;
+    return act;
+#endif
+}
+
+static ETHR_INLINE long
+ethr_native_atomic_cmpxchg_relb(ethr_native_atomic_t *var, long new, long exp)
+{
+#ifdef AO_HAVE_compare_and_swap_release
+    long act;
+    do {
+	if (AO_compare_and_swap_release(&var->counter, (AO_t) exp, (AO_t) new))
+	    return exp;
+	act = (long) AO_load(&var->counter);
+    } while (act == exp);
+    return act;
+#else
+    ETHR_MEMORY_BARRIER;
+    return ethr_native_atomic_cmpxchg(var, new, exp);
+#endif
+}
+
+
+#endif
+
+#endif
+
+#endif
diff --git a/erts/include/internal/libatomic_ops/ethread.h b/erts/include/internal/libatomic_ops/ethread.h
new file mode 100644
index 0000000000..ee73ba73bc
--- /dev/null
+++ b/erts/include/internal/libatomic_ops/ethread.h
@@ -0,0 +1,30 @@
+/*
+ * %CopyrightBegin%
+ *
+ * Copyright Ericsson AB 2010. All Rights Reserved.
+ *
+ * The contents of this file are subject to the Erlang Public License,
+ * Version 1.1, (the "License"); you may not use this file except in
+ * compliance with the License. You should have received a copy of the
+ * Erlang Public License along with this software. If not, it can be
+ * retrieved online at http://www.erlang.org/.
+ *
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * %CopyrightEnd%
+ */
+
+/*
+ * Description: Native atomics ethread support using libatomic_ops
+ * Author: Rickard Green
+ */
+
+#ifndef ETHREAD_LIBATOMIC_OPS_H__
+#define ETHREAD_LIBATOMIC_OPS_H__
+
+#include "ethr_atomic.h"
+
+#endif