diff options
Diffstat (limited to 'erts/doc/src/erl.xml')
| -rw-r--r-- | erts/doc/src/erl.xml | 293 |
1 files changed, 251 insertions, 42 deletions
diff --git a/erts/doc/src/erl.xml b/erts/doc/src/erl.xml index bb81330fec..d11f6b0c6d 100644 --- a/erts/doc/src/erl.xml +++ b/erts/doc/src/erl.xml @@ -1,4 +1,4 @@ -<?xml version="1.0" encoding="latin1" ?> +<?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE comref SYSTEM "comref.dtd"> <comref> @@ -495,7 +495,7 @@ <c><![CDATA[werl]]></c>, not <c><![CDATA[erl]]></c> (<c><![CDATA[oldshell]]></c>). Note also that <c><![CDATA[Ctrl-Break]]></c> is used instead of <c><![CDATA[Ctrl-C]]></c> on Windows.</p> </item> - <tag><c><![CDATA[+c]]></c></tag> + <tag><marker id="+c"><c><![CDATA[+c]]></c></marker></tag> <item> <p>Disable compensation for sudden changes of system time.</p> <p>Normally, <c><![CDATA[erlang:now/0]]></c> will not immediately reflect @@ -510,6 +510,9 @@ reflect the current system time. Note that timers are based on <c><![CDATA[erlang:now/0]]></c>. If the system time jumps, timers then time out at the wrong time.</p> + <p><em>NOTE</em>: You can check whether the adjustment is enabled or + disabled by calling + <seealso marker="erlang#system_info_tolerant_timeofday">erlang:system_info(tolerant_timeofday)</seealso>.</p> </item> <tag><c><![CDATA[+d]]></c></tag> <item> @@ -522,9 +525,10 @@ core dump and no crash dump if an internal error is detected.</p> <p>Calling <c>erlang:halt/1</c> with a string argument will still - produce a crash dump.</p> + produce a crash dump. On Unix systems, sending an emulator process + a SIGUSR1 signal will also force a crash dump.</p> </item> - <tag><c><![CDATA[+e Number]]></c></tag> + <tag><marker id="+e"><c><![CDATA[+e Number]]></c></marker></tag> <item> <p>Set max number of ETS tables.</p> </item> @@ -535,16 +539,44 @@ </item> <tag><marker id="file_name_encoding"></marker><c><![CDATA[+fnl]]></c></tag> <item> - <p>The VM works with file names as if they are encoded using the ISO-latin-1 encoding, disallowing Unicode characters with codepoints beyond 255. This is default on operating systems that have transparent file naming, i.e. all Unixes except MacOSX.</p> - </item> - <tag><c><![CDATA[+fnu]]></c></tag> - <item> - <p>The VM works with file names as if they are encoded using UTF-8 (or some other system specific Unicode encoding). This is the default on operating systems that enforce Unicode encoding, i.e. Windows and MacOSX.</p> - <p>By enabling Unicode file name translation on systems where this is not default, you open up to the possibility that some file names can not be interpreted by the VM and therefore will be returned to the program as raw binaries. The option is therefore considered experimental.</p> - </item> - <tag><c><![CDATA[+fna]]></c></tag> - <item> - <p>Selection between <c>+fnl</c> and <c>+fnu</c> is done based on the current locale settings in the OS, meaning that if you have set your terminal for UTF-8 encoding, the filesystem is expected to use the same encoding for filenames (use with care).</p> + <p>The VM works with file names as if they are encoded using the ISO-latin-1 encoding, disallowing Unicode characters with codepoints beyond 255.</p> + <p>See <seealso marker="stdlib:unicode_usage#unicode_file_names">STDLIB User's Guide</seealso> for more infomation about unicode file names. Note that this value also applies to command-line parameters and environment variables (see <seealso marker="stdlib:unicode_usage#unicode_in_environment_and_parameters">STDLIB User's Guide</seealso>).</p> + </item> + <tag><c><![CDATA[+fnu[{w|i|e}]]]></c></tag> + <item> + <p>The VM works with file names as if they are encoded using + UTF-8 (or some other system specific Unicode encoding). This + is the default on operating systems that enforce Unicode + encoding, i.e. Windows and MacOS X.</p> + <p>The <c>+fnu</c> switch can be followed by <c>w</c>, + <c>i</c>, or <c>e</c> to control the way wrongly encoded file + names are to be reported. <c>w</c> means that a warning is + sent to the <c>error_logger</c> whenever a wrongly encoded + file name is "skipped" in directory listings, <c>i</c> means + that those wrongly encoded file names are silently ignored and + <c>e</c> means that the API function will return an error + whenever a wrongly encoded file (or directory) name is + encountered. <c>w</c> is the default. Note that + <c>file:read_link/1</c> will always return an error if the + link points to an invalid file name.</p> + <p>See <seealso marker="stdlib:unicode_usage#unicode_file_names">STDLIB User's Guide</seealso> for more infomation about unicode file names. Note that this value also applies to command-line parameters and environment variables (see <seealso marker="stdlib:unicode_usage#unicode_in_environment_and_parameters">STDLIB User's Guide</seealso>).</p> + </item> + <tag><c><![CDATA[+fna[{w|i|e}]]]></c></tag> + <item> + <p>Selection between <c>+fnl</c> and <c>+fnu</c> is done based + on the current locale settings in the OS, meaning that if you + have set your terminal for UTF-8 encoding, the filesystem is + expected to use the same encoding for file names. This is + default on all operating systems except MacOS X and + Windows.</p> + <p>The <c>+fna</c> switch can be followed by <c>w</c>, + <c>i</c>, or <c>e</c>. This will have effect if the locale + settings cause the behavior of <c>+fnu</c> to be selected. + See the description of <c>+fnu</c> above. If the locale + settings cause the behavior of <c>+fnl</c> to be selected, + then <c>w</c>, <c>i</c>, or <c>e</c> will not have any + effect.</p> + <p>See <seealso marker="stdlib:unicode_usage#unicode_file_names">STDLIB User's Guide</seealso> for more infomation about unicode file names. Note that this value also applies to command-line parameters and environment variables (see <seealso marker="stdlib:unicode_usage#unicode_in_environment_and_parameters">STDLIB User's Guide</seealso>).</p> </item> <tag><c><![CDATA[+hms Size]]></c></tag> <item> @@ -571,9 +603,9 @@ </item> <tag><c><![CDATA[+L]]></c></tag> <item> - <p>Don't load information about source filenames and line numbers. + <p>Don't load information about source file names and line numbers. This will save some memory, but exceptions will not contain - information about the filenames and line numbers. + information about the file names and line numbers. </p> </item> <tag><marker id="erts_alloc"><c><![CDATA[+MFlag Value]]></c></marker></tag> @@ -615,7 +647,7 @@ debugging.</item> </taglist> </item> - <tag><marker id="+pc"/><marker id="max_processes"><c><![CDATA[+pc Range]]></c></marker></tag> + <tag><marker id="+pc"/><marker id="printable_character_range"><c><![CDATA[+pc Range]]></c></marker></tag> <item> <p>Sets the range of characters that the system will consider printable in heuristic detection of strings. This typically affects the shell, debugger and io:format functions (when ~tp is used in the format string).</p> <p>Currently two values for the <c>Range</c> are supported: @@ -637,10 +669,11 @@ <p>Se also <seealso marker="stdlib:io#printable_range/0"> io:printable_range/0</seealso>.</p> </item> - <tag><marker id="+P"/><marker id="max_processes"><c><![CDATA[+P Number]]></c></marker></tag> + <tag><marker id="+P"/><marker id="max_processes"><c><![CDATA[+P Number|legacy]]></c></marker></tag> <item> <p>Sets the maximum number of simultaneously existing processes for this - system. Valid range for <c>Number</c> is <c>[1024-134217727]</c></p> + system if a <c>Number</c> is passed as value. Valid range for + <c>Number</c> is <c>[1024-134217727]</c></p> <p><em>NOTE</em>: The actual maximum chosen may be much larger than the <c>Number</c> passed. Currently the runtime system often, but not always, chooses a value that is a power of 2. This might, @@ -648,11 +681,19 @@ checked by calling <seealso marker="erlang#system_info_process_limit">erlang:system_info(process_limit)</seealso>.</p> <p>The default value is <c>262144</c></p> + <p>If <c>legacy</c> is passed as value, the legacy algorithm for + allocation of process identifiers will be used. Using the legacy + algorithm, identifiers will be allocated in a strictly increasing + fashion until largest possible identifier has been reached. Note that + this algorithm suffers from performance issues and can under certain + circumstances be extremely expensive. The legacy algoritm is deprecated, + and the <c>legacy</c> option is scheduled for removal in OTP-R18.</p> </item> - <tag><marker id="+Q"/><marker id="max_ports"><c><![CDATA[+Q Number]]></c></marker></tag> + <tag><marker id="+Q"/><marker id="max_ports"><c><![CDATA[+Q Number|legacy]]></c></marker></tag> <item> <p>Sets the maximum number of simultaneously existing ports for this - system. Valid range for <c>Number</c> is <c>[1024-134217727]</c></p> + system if a Number is passed as value. Valid range for <c>Number</c> + is <c>[1024-134217727]</c></p> <p><em>NOTE</em>: The actual maximum chosen may be much larger than the actual <c>Number</c> passed. Currently the runtime system often, but not always, chooses a value that is a power of 2. This might, @@ -671,6 +712,13 @@ for setting the maximum number of simultaneously existing ports. This environment variable is deprecated, and scheduled for removal in OTP-R17, but can still be used.</p> + <p>If <c>legacy</c> is passed as value, the legacy algorithm for + allocation of port identifiers will be used. Using the legacy + algorithm, identifiers will be allocated in a strictly increasing + fashion until largest possible identifier has been reached. Note that + this algorithm suffers from performance issues and can under certain + circumstances be extremely expensive. The legacy algoritm is deprecated, + and the <c>legacy</c> option is scheduled for removal in OTP-R18.</p> </item> <tag><marker id="compat_rel"><c><![CDATA[+R ReleaseNumber]]></c></marker></tag> <item> @@ -712,22 +760,111 @@ </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 - threads to set online when SMP support has been enabled. - Valid range for both values are 1-1024. If the - Erlang runtime system is able to determine the amount - of logical processors configured and logical processors available, - <c>Schedulers</c> will default to logical processors configured, - and <c>SchedulersOnline</c> will default to logical processors - available; otherwise, the default values will be 1. <c>Schedulers</c> - may be omitted if <c>:SchedulerOnline</c> is not and vice versa. The - amount of schedulers online can be changed at run time via + <p>Sets the number of scheduler threads to create and scheduler + threads to set online when SMP support has been enabled. The maximum for + both values is 1024. If the Erlang runtime system is able to determine the + amount of logical processors configured and logical processors available, + <c>Schedulers</c> will default to logical processors configured, and + <c>SchedulersOnline</c> will default to logical processors available; + otherwise, the default values will be 1. <c>Schedulers</c> may be omitted + if <c>:SchedulerOnline</c> is not and vice versa. The number of schedulers + online can be changed at run time via + <seealso marker="erlang#system_flag_schedulers_online">erlang:system_flag(schedulers_online, SchedulersOnline)</seealso>. + </p> + <p>If <c>Schedulers</c> or <c>SchedulersOnline</c> is specified as a + negative number, the value is subtracted from the default number of + logical processors configured or logical processors available, respectively. + </p> + <p>Specifying the value 0 for <c>Schedulers</c> or <c>SchedulersOnline</c> + resets the number of scheduler threads or scheduler threads online respectively + to its default value. + </p> + <p>This option is ignored if the emulator doesn't have + SMP support enabled (see the <seealso marker="#smp">-smp</seealso> + flag).</p> + </item> + <tag><marker id="+SP"><c><![CDATA[+SP SchedulersPercentage:SchedulersOnlinePercentage]]></c></marker></tag> + <item> + <p>Similar to <seealso marker="#+S">+S</seealso> but uses percentages to set the + number of scheduler threads to create, based on logical processors configured, + and scheduler threads to set online, based on logical processors available, when + SMP support has been enabled. Specified values must be greater than 0. For example, + <c>+SP 50:25</c> sets the number of scheduler threads to 50% of the logical processors + configured and the number of scheduler threads online to 25% of the logical processors available. + <c>SchedulersPercentage</c> may be omitted if <c>:SchedulersOnlinePercentage</c> is + not and vice versa. The number of schedulers online can be changed at run time via <seealso marker="erlang#system_flag_schedulers_online">erlang:system_flag(schedulers_online, SchedulersOnline)</seealso>. </p> - <p>This flag will be ignored if the emulator doesn't have + <p>This option interacts with <seealso marker="#+S">+S</seealso> settings. + For example, on a system with 8 logical cores configured and 8 logical cores + available, the combination of the options <c>+S 4:4 +SP 50:25</c> (in either order) + results in 2 scheduler threads (50% of 4) and 1 scheduler thread online (25% of 4). + </p> + <p>This option is ignored if the emulator doesn't have SMP support enabled (see the <seealso marker="#smp">-smp</seealso> flag).</p> </item> + <tag><marker id="+SDcpu"><c><![CDATA[+SDcpu DirtyCPUSchedulers:DirtyCPUSchedulersOnline]]></c></marker></tag> + <item> + <p>Sets the number of dirty CPU scheduler threads to create and dirty + CPU scheduler threads to set online when threading support has been + enabled. The maximum for both values is 1024, and each value is further + limited by the settings for normal schedulers: the number of dirty CPU + scheduler threads created cannot exceed the number of normal scheduler + threads created, and the number of dirty CPU scheduler threads online + cannot exceed the number of normal scheduler threads online (see the + <seealso marker="#+S">+S</seealso> and <seealso marker="#+SP">+SP</seealso> + flags for more details). By default, the number of dirty CPU scheduler + threads created equals the number of normal scheduler threads created, + and the number of dirty CPU scheduler threads online equals the number + of normal scheduler threads online. <c>DirtyCPUSchedulers</c> may be + omitted if <c>:DirtyCPUSchedulersOnline</c> is not and vice versa. The + number of dirty CPU schedulers online can be changed at run time via + <seealso marker="erlang#system_flag_dirty_cpu_schedulers_online">erlang:system_flag(dirty_cpu_schedulers_online, DirtyCPUSchedulersOnline)</seealso>. + </p> + <p>This option is ignored if the emulator doesn't have threading support + enabled. Currently, <em>this option is experimental</em> and is supported only + if the emulator was configured and built with support for dirty schedulers + enabled (it's disabled by default). + </p> + </item> + <tag><marker id="+SDPcpu"><c><![CDATA[+SDPcpu DirtyCPUSchedulersPercentage:DirtyCPUSchedulersOnlinePercentage]]></c></marker></tag> + <item> + <p>Similar to <seealso marker="#+SDcpu">+SDcpu</seealso> but uses percentages to set the + number of dirty CPU scheduler threads to create and number of dirty CPU scheduler threads + to set online when threading support has been enabled. Specified values must be greater + than 0. For example, <c>+SDPcpu 50:25</c> sets the number of dirty CPU scheduler threads + to 50% of the logical processors configured and the number of dirty CPU scheduler threads + online to 25% of the logical processors available. <c>DirtyCPUSchedulersPercentage</c> may + be omitted if <c>:DirtyCPUSchedulersOnlinePercentage</c> is not and vice versa. The + number of dirty CPU schedulers online can be changed at run time via + <seealso marker="erlang#system_flag_dirty_cpu_schedulers_online">erlang:system_flag(dirty_cpu_schedulers_online, DirtyCPUSchedulersOnline)</seealso>. + </p> + <p>This option interacts with <seealso marker="#+SDcpu">+SDcpu</seealso> settings. + For example, on a system with 8 logical cores configured and 8 logical cores available, + the combination of the options <c>+SDcpu 4:4 +SDPcpu 50:25</c> (in either order) results + in 2 dirty CPU scheduler threads (50% of 4) and 1 dirty CPU scheduler thread online (25% of 4). + </p> + <p>This option is ignored if the emulator doesn't have threading support + enabled. Currently, <em>this option is experimental</em> and is supported only + if the emulator was configured and built with support for dirty schedulers + enabled (it's disabled by default). + </p> + </item> + <tag><marker id="+SDio"><c><![CDATA[+SDio IOSchedulers]]></c></marker></tag> + <item> + <p>Sets the number of dirty I/O scheduler threads to create when threading + support has been enabled. The valid range is 0-1024. By default, the number + of dirty I/O scheduler threads created is 10, same as the default number of + threads in the <seealso marker="#async_thread_pool_size">async thread pool + </seealso>. + </p> + <p>This option is ignored if the emulator doesn't have threading support + enabled. Currently, <em>this option is experimental</em> and is supported only + if the emulator was configured and built with support for dirty schedulers + enabled (it's disabled by default). + </p> + </item> <tag><c><![CDATA[+sFlag Value]]></c></tag> <item> <p>Scheduling specific flags.</p> @@ -877,6 +1014,10 @@ when schedulers frequently run out of work. When disabled, the frequency with which schedulers run out of work will not be taken into account by the load balancing logic. + <br/> <c>+scl false</c> is similar to + <seealso marker="#+sub">+sub true</seealso> with the difference + that <c>+sub true</c> also will balance scheduler utilization + between schedulers. </p> </item> <tag><marker id="+sct"><c>+sct CpuTopology</c></marker></tag> @@ -1001,6 +1142,37 @@ <p>For more information, see <seealso marker="erlang#system_info_cpu_topology">erlang:system_info(cpu_topology)</seealso>.</p> </item> + <tag><marker id="+secio"><c>+secio true|false</c></marker></tag> + <item> + <p>Enable or disable eager check I/O scheduling. The default + is currently <c>false</c>, but will most likely be changed + to <c>true</c> in OTP 18. The behaviour before this flag + was introduced corresponds to <c>+secio false</c>.</p> + <p>The flag effects when schedulers will check for I/O + operations possible to execute, and when such I/O operations + will execute. As the name of the parameter implies, + schedulers will be more eager to check for I/O when + <c>true</c> is passed. This however also implies that + execution of outstanding I/O operation will not be + prioritized to the same extent as when <c>false</c> is + passed.</p> + <p><seealso marker="erlang#system_info_eager_check_io"><c>erlang:system_info(eager_check_io)</c></seealso> + returns the value of this parameter used when starting the VM.</p> + </item> + <tag><marker id="+sfwi"><c>+sfwi Interval</c></marker></tag> + <item> + <p>Set scheduler forced wakeup interval. All run queues will + be scanned each <c>Interval</c> milliseconds. While there are + sleeping schedulers in the system, one scheduler will be woken + for each non-empty run queue found. An <c>Interval</c> of zero + disables this feature, which also is the default. + </p> + <p>This feature has been introduced as a temporary workaround + for lengthy executing native code, and native code that do not + bump reductions properly in OTP. When these bugs have be fixed + the <c>+sfwi</c> flag will be removed. + </p> + </item> <tag><marker id="+stbt"><c>+stbt BindType</c></marker></tag> <item> <p>Try to set scheduler bind type. The same as the @@ -1009,6 +1181,43 @@ documentation of the <seealso marker="#+sbt">+sbt</seealso> flag. </p> </item> + <tag><marker id="+sub"><c>+sub true|false</c></marker></tag> + <item> + <p>Enable or disable + <seealso marker="erts:erlang#statistics_scheduler_wall_time">scheduler + utilization</seealso> balancing of load. By default scheduler + utilization balancing is disabled and instead scheduler + compaction of load is enabled which will strive for a load + distribution which causes as many scheduler threads as possible + to be fully loaded (i.e., not run out of work). When scheduler + utilization balancing is enabled the system will instead try to + balance scheduler utilization between schedulers. That is, + strive for equal scheduler utilization on all schedulers. + <br/> <c>+sub true</c> is only supported on + systems where the runtime system detects and use a monotonically + increasing high resolution clock. On other systems, the runtime + system will fail to start. + <br/> <c>+sub true</c> implies + <seealso marker="#+scl">+scl false</seealso>. The difference + between <c>+sub true</c> and <c>+scl false</c> is that + <c>+scl false</c> will not try to balance the scheduler + utilization. + </p> + </item> + <tag><marker id="+swct"><c>+swct very_eager|eager|medium|lazy|very_lazy</c></marker></tag> + <item> + <p> + Set scheduler wake cleanup threshold. Default is <c>medium</c>. + This flag controls how eager schedulers should be requesting + wake up due to certain cleanup operations. When a lazy setting + is used, more outstanding cleanup operations can be left undone + while a scheduler is idling. When an eager setting is used, + schedulers will more frequently be woken, potentially increasing + CPU-utilization. + </p> + <p><em>NOTE:</em> This flag may be removed or changed at any time without prior notice. + </p> + </item> <tag><marker id="+sws"><c>+sws default|legacy</c></marker></tag> <item> <p> @@ -1034,18 +1243,18 @@ <tag><marker id="+spp"><c>+spp Bool</c></marker></tag> <item> <p>Set default scheduler hint for port parallelism. If set to - <c>true</c>, the VM will schedule port tasks when it by this can - improve the parallelism in the system. If set to <c>false</c>, - the VM will try to perform port tasks immediately and by this - improve latency at the expense of parallelism. If this - flag has not been passed, the default scheduler hint for port - parallelism is currently <c>false</c>. The default used can be - inspected in runtime by calling - <seealso marker="erlang#system_info_port_parallelism">erlang:system_info(port_parallelism)</seealso>. + <c>true</c>, the VM will schedule port tasks when doing so will + improve parallelism in the system. If set to <c>false</c>, the VM + will try to perform port tasks immediately, improving latency at the + expense of parallelism. If this flag has not been passed, the + default scheduler hint for port parallelism is currently + <c>false</c>. The default used can be inspected in runtime by + calling <seealso + marker="erlang#system_info_port_parallelism">erlang:system_info(port_parallelism)</seealso>. The default can be overriden on port creation by passing the <seealso marker="erlang#open_port_parallelism">parallelism</seealso> - option to - <seealso marker="erlang#open_port/2">open_port/2</seealso></p>. + option to <seealso + marker="erlang#open_port/2">open_port/2</seealso></p>. </item> <tag><marker id="sched_thread_stack_size"><c><![CDATA[+sss size]]></c></marker></tag> <item> |