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-rw-r--r--HOWTO/INSTALL.md64
1 files changed, 38 insertions, 26 deletions
diff --git a/HOWTO/INSTALL.md b/HOWTO/INSTALL.md
index 53b1b8cd8a..f8900c501b 100644
--- a/HOWTO/INSTALL.md
+++ b/HOWTO/INSTALL.md
@@ -417,22 +417,33 @@ important when building Erlang/OTP. By default the VM will refuse to build
if native atomic memory operations are not available.
Erlang/OTP itself provides implementations of native atomic memory operations
-that can be used when compiling with a `gcc` compatible compiler on 32-bit
-and 64-bit x86, 32-bit and 64-bit SPARC V9, and 32-bit PowerPC. When compiling
-with a `gcc` compatible compiler on other architectures, the VM may be able to
-make use of native atomic operations using the `__sync_*` primitives, but this
-should only be used as a last resort since this wont give you optimal
-performance. When compiling on Windows using a MicroSoft Visual C++ compiler
-native atomic memory operations are provided by Windows APIs.
-
-You are recommended to use the native atomic implementation provided by
-Erlang/OTP, or the API provided by Windows. If these do not provide native
-atomics on your platform, you are recommended to build and install
-[libatomic_ops][] before building Erlang/OTP. The `libatomic_ops` library
-provides native atomic memory operations for a variety of platforms and
-compilers. When building Erlang/OTP you need to inform the build system of
-where the `libatomic_ops` library is installed using the
-`--with-libatomic_ops=PATH` configure switch.
+that can be used when compiling with a `gcc` compatible compiler for 32/64-bit
+x86, 32/64-bit SPARC V9, 32-bit PowerPC, or 32-bit Tile. When compiling with
+a `gcc` compatible compiler for other architectures, the VM may be able to make
+use of native atomic operations using the `__atomic_*` builtins (may be
+available when using a `gcc` of at least version 4.7) and/or using the
+`__sync_*` builtins (may be available when using a `gcc` of at least version
+4.1). If only the `gcc`'s `__sync_*` builtins are available, the performance
+will suffer. Such a configuration should only be used as a last resort. When
+compiling on Windows using a MicroSoft Visual C++ compiler native atomic
+memory operations are provided by Windows APIs.
+
+Native atomic implementation in the order preferred:
+1. The implementation provided by Erlang/OTP.
+2. The API provided by Windows.
+3. The implementation based on the `gcc` `__atomic_*` builtins.
+4. If none of the above are available for your architecture/compiler, you
+ are recommended to build and install [libatomic_ops][] before building
+ Erlang/OTP. The `libatomic_ops` library provides native atomic memory
+ operations for a variety of architectures and compilers. When building
+ Erlang/OTP you need to inform the build system of where the
+ `libatomic_ops` library is installed using the
+ `--with-libatomic_ops=PATH` `configure` switch.
+5. As a last resort, the implementation solely based on the `gcc`
+ `__sync_*` builtins. This will however cause lots of expensive and
+ unnecessary memory barrier instructions to be issued. That is,
+ performance will suffer. The `configure` script will warn at the end
+ of its execution if it cannot find any other alternative than this.
### Building ###
@@ -849,18 +860,19 @@ Copyright and License
%CopyrightBegin%
-Copyright Ericsson AB 1998-2014. All Rights Reserved.
+Copyright Ericsson AB 1998-2015. 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/.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
-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.
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
%CopyrightEnd%