diff options
Diffstat (limited to 'erts/doc/src/erl.xml')
| -rw-r--r-- | erts/doc/src/erl.xml | 58 |
1 files changed, 56 insertions, 2 deletions
diff --git a/erts/doc/src/erl.xml b/erts/doc/src/erl.xml index bb741c7836..f477280a6f 100644 --- a/erts/doc/src/erl.xml +++ b/erts/doc/src/erl.xml @@ -41,6 +41,26 @@ to scroll back to text which has scrolled off the screen. The <c><![CDATA[erl]]></c> program must be used, however, in pipelines or if you want to redirect standard input or output.</p> + <note><p>As of ERTS version 5.8 (OTP-R14A) the runtime system will by + default bind schedulers to logical processors using the + <c>default_bind</c> bind type if the amount of schedulers are + at least equal to the amount of logical processors configured, + binding of schedulers is supported, and a CPU topology is + available at startup. + </p><p> + If the Erlang runtime system is the only operating system + process that binds threads to logical processors, this + improves the performance of the runtime system. However, + if other operating system processes (as for example + another Erlang runtime system) also bind threads to + logical processors, there might be a performance penalty + instead. If this is the case you, are are advised to + unbind the schedulers using the + <seealso marker="#+sbt">+sbtu</seealso> command line argument, + or by invoking + <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, + unbound)</seealso>.</p> + </note> </description> <funcs> <func> @@ -583,6 +603,24 @@ <item> <p>Force ets memory block to be moved on realloc.</p> </item> + <tag><marker id="+rg"><c><![CDATA[+rg ReaderGroupsLimit]]></c></marker></tag> + <item> + <p>Limits the amount of reader groups used by read/write locks + optimized for read operations in the Erlang runtime system. By + default the reader groups limit equals 8.</p> + <p>When the amount of schedulers is less than or equal to the reader + groups limit, each scheduler has its own reader group. When the + amount of schedulers is larger than the reader groups limit, + schedulers share reader groups. Shared reader groups degrades + read lock and read unlock performance while a large amount of + reader groups degrades write lock performance, so the limit is a + tradeoff between performance for read operations and performance + for write operations. Each reader group currently consumes 64 byte + in each read/write lock. Also note that a runtime system using + shared reader groups benefits from <seealso marker="#+sbt">binding + schedulers to logical processors</seealso>, since the reader groups + are distributed better between schedulers.</p> + </item> <tag><marker id="+S"><c><![CDATA[+S Schedulers:SchedulerOnline]]></c></marker></tag> <item> <p>Sets the amount of scheduler threads to create and scheduler @@ -647,8 +685,8 @@ <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, default_bind)</seealso>. </p></item> </taglist> - <p>Binding of schedulers are currently only supported on newer - Linux and Solaris systems.</p> + <p>Binding of schedulers is currently only supported on newer + Linux, Solaris, and Windows systems.</p> <p>If no CPU topology is available when the <c>+sbt</c> flag is processed and <c>BindType</c> is any other type than <c>u</c>, the runtime system will fail to start. CPU @@ -657,6 +695,22 @@ that the <c>+sct</c> flag may have to be passed before the <c>+sbt</c> flag on the command line (in case no CPU topology has been automatically detected).</p> + <p>The runtime system will by default bind schedulers to logical + processors using the <c>default_bind</c> bind type if the amount + of schedulers are at least equal to the amount of logical + processors configured, binding of schedulers is supported, + and a CPU topology is available at startup. + </p> + <p><em>NOTE:</em> If the Erlang runtime system is the only operating + system process that binds threads to logical processors, this + improves the performance of the runtime system. However, if other + operating system processes (as for example another Erlang runtime + system) also bind threads to logical processors, there might be a + performance penalty instead. If this is the case you, are advised + to unbind the schedulers using the <c>+sbtu</c> command line + argument, or by invoking + <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, + unbound)</seealso>.</p> <p>For more information, see <seealso marker="erlang#system_flag_scheduler_bind_type">erlang:system_flag(scheduler_bind_type, SchedulerBindType)</seealso>. </p> |