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-rw-r--r--erts/doc/src/Makefile11
-rw-r--r--erts/doc/src/atomics.xml183
-rw-r--r--erts/doc/src/counters.xml142
-rw-r--r--erts/doc/src/ref_man.xml2
-rw-r--r--erts/doc/src/specs.xml2
5 files changed, 333 insertions, 7 deletions
diff --git a/erts/doc/src/Makefile b/erts/doc/src/Makefile
index fccdd744f3..40f74b78ff 100644
--- a/erts/doc/src/Makefile
+++ b/erts/doc/src/Makefile
@@ -53,19 +53,16 @@ XML_REF3_EFILES = \
erl_tracer.xml \
init.xml \
persistent_term.xml \
+ atomics.xml \
+ counters.xml \
zlib.xml
XML_REF3_FILES = \
+ $(XML_REF3_EFILES) \
driver_entry.xml \
erl_nif.xml \
- erl_tracer.xml \
erl_driver.xml \
- erl_prim_loader.xml \
- erlang.xml \
- erts_alloc.xml \
- init.xml \
- persistent_term.xml \
- zlib.xml
+ erts_alloc.xml
XML_PART_FILES = \
part.xml
diff --git a/erts/doc/src/atomics.xml b/erts/doc/src/atomics.xml
new file mode 100644
index 0000000000..3fca92fb97
--- /dev/null
+++ b/erts/doc/src/atomics.xml
@@ -0,0 +1,183 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE erlref SYSTEM "erlref.dtd">
+
+<erlref>
+ <header>
+ <copyright>
+ <year>2018</year>
+ <holder>Ericsson AB. All Rights Reserved.</holder>
+ </copyright>
+ <legalnotice>
+ 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
+
+ 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.
+ </legalnotice>
+
+ <title>atomics</title>
+ </header>
+ <module>atomics</module>
+ <modulesummary>Atomic Functions</modulesummary>
+ <description>
+ <p>This module provides a set of functions to do atomic operations towards
+ mutable atomic variables. The implementation utilizes only
+ atomic hardware instructions without any software level locking, which makes
+ it very efficient for concurrent access. The atomics are organized into
+ arrays with the follwing semantics:</p>
+ <list type="bulleted">
+ <item>
+ <p>Atomics are 64 bit integers.</p>
+ </item>
+ <item>
+ <p>Atomics can be represented as either signed or unsigned.</p>
+ </item>
+ <item>
+ <p>Atomics wrap around at overflow and underflow operations.</p>
+ </item>
+ <item>
+ <p>All operations guarantee atomicity. No intermediate results can be
+ seen. The result of one mutation can only be the input to one
+ following mutation.</p>
+ </item>
+ <item>
+ <p>All atomic operations are mutually ordered. If atomic B is updated
+ <em>after</em> atomic A, then that is how it will appear to any
+ concurrent readers. No one can read the new value of B and then read the
+ old value of A.</p>
+ </item>
+ <item>
+ <p>Indexes into atomic arrays are one-based. An atomic array of
+ arity N contains N atomics with index from 1 to N.</p>
+ </item>
+ </list>
+ </description>
+
+ <datatypes>
+ <datatype>
+ <name name="atomics_ref"/>
+ <desc><p>Identifies an atomic array returned from
+ <seealso marker="#new/2"><c>new/2</c></seealso>.</p>
+ </desc>
+ </datatype>
+ </datatypes>
+
+ <funcs>
+ <func>
+ <name name="new" arity="2"/>
+ <fsummary>Create atomic array</fsummary>
+ <desc>
+ <p>Create a new atomic array of <c><anno>Arity</anno></c> atomics.</p>
+ <p>Argument <c><anno>Opts</anno></c> is a list of the following possible
+ options:</p>
+ <taglist>
+ <tag><c>{signed, boolean()}</c></tag>
+ <item><p>Indicate if the elements of the array will be treated
+ as signed or unsigned integers. Default is <c>true</c> (signed).</p>
+ <p>The integer interval for signed atomics are from <c>-(1 bsl 63)</c>
+ to <c>(1 bsl 63)-1</c> and for unsigned atomics from <c>0</c> to <c>(1
+ bsl 64)-1</c>.</p>
+ </item>
+ </taglist>
+ </desc>
+ </func>
+
+ <func>
+ <name name="put" arity="3"/>
+ <fsummary>Set atomic value</fsummary>
+ <desc>
+ <p>Set atomic to <c><anno>Value</anno></c>.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="get" arity="2"/>
+ <fsummary>Read atomic value</fsummary>
+ <desc>
+ <p>Read atomic value.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="add" arity="3"/>
+ <fsummary>Add to atomic</fsummary>
+ <desc>
+ <p>Add <c><anno>Incr</anno></c> to atomic.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="add_get" arity="3"/>
+ <fsummary>Atomic add and get</fsummary>
+ <desc>
+ <p>Atomic addition and return of the result.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="sub" arity="3"/>
+ <fsummary>Subtract from atomic</fsummary>
+ <desc>
+ <p>Subtract <c><anno>Decr</anno></c> from atomic.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="sub_get" arity="3"/>
+ <fsummary>Atomic sub and get</fsummary>
+ <desc>
+ <p>Atomic subtraction and return of the result.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="exchange" arity="3"/>
+ <fsummary>Atomic exchange.</fsummary>
+ <desc>
+ <p>Atomically replaces the value of the atomic with
+ <c><anno>Desired</anno></c> and returns the value it held
+ previously.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="compare_exchange" arity="4"/>
+ <fsummary>Atomic compare and exchange.</fsummary>
+ <desc>
+ <p>Atomically compares the atomic with <c><anno>Expected</anno></c>,
+ and if those are equal, set atomic to <c><anno>Desired</anno></c>.
+ Returns <c>ok</c> if <c><anno>Desired</anno></c> was written. Returns
+ the actual atomic value if not equal to <c><anno>Expected</anno></c>.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="info" arity="1"/>
+ <fsummary>Get information about atomic array.</fsummary>
+ <desc>
+ <p>Return information about an atomic array in a map. The map
+ has the following keys:</p>
+ <taglist>
+ <tag><c>size</c></tag>
+ <item><p>The number of atomics in the array.</p></item>
+ <tag><c>max</c></tag>
+ <item><p>The highest possible value an atomic in this array can
+ hold.</p></item>
+ <tag><c>min</c></tag>
+ <item><p>The lowest possible value an atomic in this array can
+ hold.</p></item>
+ <tag><c>memory</c></tag>
+ <item><p>Approximate memory consumption for the array in
+ bytes.</p></item>
+ </taglist>
+ </desc>
+ </func>
+
+ </funcs>
+</erlref>
diff --git a/erts/doc/src/counters.xml b/erts/doc/src/counters.xml
new file mode 100644
index 0000000000..85eedfdadc
--- /dev/null
+++ b/erts/doc/src/counters.xml
@@ -0,0 +1,142 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE erlref SYSTEM "erlref.dtd">
+
+<erlref>
+ <header>
+ <copyright>
+ <year>2018</year>
+ <holder>Ericsson AB. All Rights Reserved.</holder>
+ </copyright>
+ <legalnotice>
+ 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
+
+ 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.
+ </legalnotice>
+
+ <title>counters</title>
+ </header>
+ <module>counters</module>
+ <modulesummary>Counter Functions</modulesummary>
+ <description>
+ <p>This module provides a set of functions to do operations towards
+ shared mutable counter variables. The implementation does not utilize any
+ software level locking, which makes it very efficient for concurrent
+ access. The counters are organized into arrays with the follwing
+ semantics:</p>
+ <list type="bulleted">
+ <item>
+ <p>Counters are 64 bit signed integers.</p>
+ </item>
+ <item>
+ <p>Counters wrap around at overflow and underflow operations.</p>
+ </item>
+ <item><p>Counters are initialized to zero and can then only be written to
+ by adding or subtracting.</p>
+ </item>
+ <item>
+ <p>Write operations guarantee atomicity. No intermediate results can be
+ seen from a single write operation.</p>
+ </item>
+ <item>
+ <p>Two types of counter arrays can be created with options <c>atomics</c> or
+ <c>write_concurrency</c>. The <c>atomics</c> counters have good allround
+ performance with nice consistent semantics while
+ <c>write_concurrency</c> counters offers even better concurrent
+ write performance at the expense of some potential read
+ inconsistencies. See <seealso marker="#new/2"><c>new/2</c></seealso>.</p>
+ </item>
+ <item>
+ <p>Indexes into counter arrays are one-based. A counter array of
+ size N contains N counters with index from 1 to N.</p>
+ </item>
+ </list>
+ </description>
+
+ <datatypes>
+ <datatype>
+ <name name="counters_ref"/>
+ <desc><p>Identifies a counter array returned from
+ <seealso marker="#new/2"><c>new/2</c></seealso>.</p>
+ </desc>
+ </datatype>
+ </datatypes>
+
+ <funcs>
+ <func>
+ <name name="new" arity="2"/>
+ <fsummary>Create counter array</fsummary>
+ <desc>
+ <p>Create a new counter array of <c><anno>Size</anno></c> counters.</p>
+ <p>Argument <c><anno>Opts</anno></c> is a list of the following possible
+ options:</p>
+ <taglist>
+ <tag><c>atomics</c> (Default)</tag>
+ <item><p>Counters will be sequentially consistent. If write
+ operation A is done sequencially before write operation B, then a concurrent reader
+ may see none of them, only A, or both A and B. It cannot see only B.</p>
+ </item>
+ <tag><c>write_concurrency</c></tag>
+ <item><p>This is an optimization to achieve very efficient concurrent
+ write operations at the expense of potential read inconsistency and memory
+ consumption per counter.</p>
+ <p>Read operations may see sequentially inconsistent results with
+ regard to concurrent write operations. Even if write operation A is done
+ sequencially before write operation B, a concurrent reader may see any
+ combination of A and B, including only B. A read operation is only
+ guaranteed to see all writes done sequentially before the read. No writes
+ are ever lost, but will eventually all be seen.</p>
+ </item>
+ </taglist>
+ </desc>
+ </func>
+
+ <func>
+ <name name="get" arity="2"/>
+ <fsummary>Read counter value</fsummary>
+ <desc>
+ <p>Read counter value.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="add" arity="3"/>
+ <fsummary>Add to counter</fsummary>
+ <desc>
+ <p>Add <c><anno>Incr</anno></c> to counter.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="sub" arity="3"/>
+ <fsummary>Subtract from counter</fsummary>
+ <desc>
+ <p>Subtract <c><anno>Decr</anno></c> from counter.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name name="info" arity="1"/>
+ <fsummary>Get information about counter array.</fsummary>
+ <desc>
+ <p>Return information about a counter array in a map. The map
+ has the following keys (at least):</p>
+ <taglist>
+ <tag><c>size</c></tag>
+ <item><p>The number of counters in the array.</p></item>
+ <tag><c>memory</c></tag>
+ <item><p>Approximate memory consumption for the array in
+ bytes.</p></item>
+ </taglist>
+ </desc>
+ </func>
+
+ </funcs>
+</erlref>
diff --git a/erts/doc/src/ref_man.xml b/erts/doc/src/ref_man.xml
index ff64aa86b8..a78aaa449e 100644
--- a/erts/doc/src/ref_man.xml
+++ b/erts/doc/src/ref_man.xml
@@ -50,5 +50,7 @@
<xi:include href="erts_alloc.xml"/>
<xi:include href="erl_nif.xml"/>
<xi:include href="erl_tracer.xml"/>
+ <xi:include href="atomics.xml"/>
+ <xi:include href="counters.xml"/>
</application>
diff --git a/erts/doc/src/specs.xml b/erts/doc/src/specs.xml
index 1ab6cdc19e..0b943e6295 100644
--- a/erts/doc/src/specs.xml
+++ b/erts/doc/src/specs.xml
@@ -6,4 +6,6 @@
<xi:include href="../specs/specs_init.xml"/>
<xi:include href="../specs/specs_persistent_term.xml"/>
<xi:include href="../specs/specs_zlib.xml"/>
+ <xi:include href="../specs/specs_atomics.xml"/>
+ <xi:include href="../specs/specs_counters.xml"/>
</specs>
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-21 15:57:53 +0000