diff options
Diffstat (limited to 'erts/doc/src/counters.xml')
| -rw-r--r-- | erts/doc/src/counters.xml | 26 |
1 files changed, 14 insertions, 12 deletions
diff --git a/erts/doc/src/counters.xml b/erts/doc/src/counters.xml index ba4a22759f..36816bd68d 100644 --- a/erts/doc/src/counters.xml +++ b/erts/doc/src/counters.xml @@ -23,13 +23,13 @@ <title>counters</title> </header> - <module>counters</module> + <module since="OTP 21.2">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 + access. The counters are organized into arrays with the following semantics:</p> <list type="bulleted"> <item> @@ -71,7 +71,7 @@ <funcs> <func> - <name name="new" arity="2"/> + <name name="new" arity="2" since="OTP 21.2"/> <fsummary>Create counter array</fsummary> <desc> <p>Create a new counter array of <c><anno>Size</anno></c> counters.</p> @@ -80,7 +80,7 @@ <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 + operation A is done sequentially 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> @@ -90,7 +90,7 @@ 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 + sequentially 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> @@ -103,11 +103,13 @@ acceptable.</p> </item> </taglist> + <p>Counters are not tied to the current process and are automatically + garbage collected when they are no longer referenced.</p> </desc> </func> <func> - <name name="get" arity="2"/> + <name name="get" arity="2" since="OTP 21.2"/> <fsummary>Read counter value</fsummary> <desc> <p>Read counter value.</p> @@ -115,7 +117,7 @@ </func> <func> - <name name="add" arity="3"/> + <name name="add" arity="3" since="OTP 21.2"/> <fsummary>Add to counter</fsummary> <desc> <p>Add <c><anno>Incr</anno></c> to counter at index @@ -124,7 +126,7 @@ </func> <func> - <name name="sub" arity="3"/> + <name name="sub" arity="3" since="OTP 21.2"/> <fsummary>Subtract from counter</fsummary> <desc> <p>Subtract <c><anno>Decr</anno></c> from counter at index @@ -133,25 +135,25 @@ </func> <func> - <name name="put" arity="3"/> + <name name="put" arity="3" since="OTP 21.2"/> <fsummary>Set counter to value</fsummary> <desc> <p>Write <c><anno>Value</anno></c> to counter at index <c><anno>Ix</anno></c>.</p> <note> <p>Despite its name, the <c>write_concurrency</c> optimization does not - improve <c>put</c>. A call to <c>put</c> is a relative heavy + improve <c>put</c>. A call to <c>put</c> is a relatively heavy operation compared to the very lightweight and scalable <seealso marker="#add/3"><c>add</c></seealso> and <seealso marker="#sub/3"> <c>sub</c></seealso>. The cost for a <c>put</c> with - <c>write_concurrency</c> is lika a <seealso marker="#get/2"><c>get</c> + <c>write_concurrency</c> is like a <seealso marker="#get/2"><c>get</c> </seealso> plus a <c>put</c> without <c>write_concurrency</c>.</p> </note> </desc> </func> <func> - <name name="info" arity="1"/> + <name name="info" arity="1" since="OTP 21.2"/> <fsummary>Get information about counter array.</fsummary> <desc> <p>Return information about a counter array in a map. The map |