Merge branch 'rickard/ethread-rewrite/OTP-8544' into dev

* rickard/ethread-rewrite/OTP-8544:
  Rewrite ethread library

1 files changed, 32 insertions, 2 deletions

diff --git a/lib/stdlib/doc/src/ets.xml b/lib/stdlib/doc/src/ets.xml
index ee1befc882..5df60a92e5 100644
--- a/lib/stdlib/doc/src/ets.xml
+++ b/lib/stdlib/doc/src/ets.xml
@@ -1039,15 +1039,22 @@ ets:select(Table,MatchSpec),</code>
               the owner terminates.</p>
           </item>
           <item>
+            <marker id="new_2_write_concurrency"></marker>
             <p><c>{write_concurrency,bool()}</c>
-              Performance tuning. Default is <c>false</c>, which means that the table
-              is optimized towards concurrent read access. An operation that
+              Performance tuning. Default is <c>false</c>. An operation that
               mutates (writes to) the table will obtain exclusive access,
               blocking any concurrent access of the same table until finished.
               If set to <c>true</c>, the table is optimized towards concurrent
               write access. Different objects of the same table can be mutated
               (and read) by concurrent processes. This is achieved to some degree
               at the expense of single access and concurrent reader performance.
+	      The <c>write_concurrency</c> option can be combined with the
+	      <seealso marker="#new_2_read_concurrency">read_concurrency</seealso>
+	      option. You typically want to combine these when large concurrent
+	      read bursts and large concurrent write bursts are common (see the
+	      documentation of the
+	      <seealso marker="#new_2_read_concurrency">read_concurrency</seealso>
+	      option for more information).
               Note that this option does not change any guarantees about 
               <seealso marker="#concurrency">atomicy and isolation</seealso>.
               Functions that makes such promises over several objects (like
@@ -1055,6 +1062,29 @@ ets:select(Table,MatchSpec),</code>
              <p>Table type <c>ordered_set</c> is not affected by this option in current
               implementation.</p>
           </item>
+          <item>
+            <marker id="new_2_read_concurrency"></marker>
+	    <p><c>{read_concurrency,bool()}</c>
+              Performance tuning. Default is <c>false</c>. When set to
+	      <c>true</c>, the table is optimized for concurrent read
+	      operations. When this option is enabled on a runtime system with
+	      SMP support, read operations become much cheaper; especially on
+	      systems with multiple physical processors. However, switching
+	      between read and write operations becomes more expensive. You
+	      typically want to enable this option when concurrent read
+	      operations are much more frequent than write operations, or when
+	      concurrent reads and writes comes in large read and write
+	      bursts (i.e., lots of reads not interrupted by writes, and lots
+	      of writes not interrupted by reads). You typically do
+	      <em>not</em> want to enable this option when the common access
+	      pattern is a few read operations interleaved with a few write
+	      operations repeatedly. In this case you will get a performance
+	      degradation by enabling this option. The <c>read_concurrency</c>
+	      option can be combined with the
+	      <seealso marker="#new_2_write_concurrency">write_concurrency</seealso>
+	      option. You typically want to combine these when large concurrent
+	      read bursts and large concurrent write bursts are common.</p>
+          </item>
         </list>
       </desc>
     </func>