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authorErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
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+<?xml version="1.0" encoding="latin1" ?>
+<!DOCTYPE cref SYSTEM "cref.dtd">
+
+<cref>
+ <header>
+ <copyright>
+ <year>2002</year><year>2009</year>
+ <holder>Ericsson AB. All Rights Reserved.</holder>
+ </copyright>
+ <legalnotice>
+ The contents of this file are subject to the Erlang Public License,
+ Version 1.1, (the "License"); you may not use this file except in
+ compliance with the License. You should have received a copy of the
+ Erlang Public License along with this software. If not, it can be
+ retrieved online at http://www.erlang.org/.
+
+ Software distributed under the License is distributed on an "AS IS"
+ basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ the License for the specific language governing rights and limitations
+ under the License.
+
+ </legalnotice>
+
+ <title>erts_alloc</title>
+ <prepared>Rickard Green</prepared>
+ <docno>1</docno>
+ <date>03-06-11</date>
+ <rev>1</rev>
+ <file>erts_alloc.xml</file>
+ </header>
+ <lib>erts_alloc</lib>
+ <libsummary>An Erlang Run-Time System internal memory allocator library.</libsummary>
+ <description>
+ <p><c>erts_alloc</c> is an Erlang Run-Time System internal memory
+ allocator library. <c>erts_alloc</c> provides the Erlang
+ Run-Time System with a number of memory allocators.</p>
+ </description>
+
+ <section>
+ <title>Allocators</title>
+ <marker id="allocators"></marker>
+ <p>Currently the following allocators are present:</p>
+ <taglist>
+ <tag><c>temp_alloc</c></tag>
+ <item>Allocator used for temporary allocations.</item>
+ <tag><c>eheap_alloc</c></tag>
+ <item>Allocator used for Erlang heap data, such as Erlang process heaps.</item>
+ <tag><c>binary_alloc</c></tag>
+ <item>Allocator used for Erlang binary data.</item>
+ <tag><c>ets_alloc</c></tag>
+ <item>Allocator used for ETS data.</item>
+ <tag><c>driver_alloc</c></tag>
+ <item>Allocator used for driver data.</item>
+ <tag><c>sl_alloc</c></tag>
+ <item>Allocator used for memory blocks that are expected to be
+ short-lived.</item>
+ <tag><c>ll_alloc</c></tag>
+ <item>Allocator used for memory blocks that are expected to be
+ long-lived, for example Erlang code.</item>
+ <tag><c>fix_alloc</c></tag>
+ <item>A very fast allocator used for some fix-sized
+ data. <c>fix_alloc</c> manages a set of memory pools from
+ which memory blocks are handed out. <c>fix_alloc</c>
+ allocates memory pools from <c>ll_alloc</c>. Memory pools
+ that have been allocated are never deallocated.</item>
+ <tag><c>std_alloc</c></tag>
+ <item>Allocator used for most memory blocks not allocated via any of
+ the other allocators described above.</item>
+ <tag><c>sys_alloc</c></tag>
+ <item>This is normally the default <c>malloc</c> implementation
+ used on the specific OS.</item>
+ <tag><c>mseg_alloc</c></tag>
+ <item>A memory segment allocator. <c>mseg_alloc</c> is used by other
+ allocators for allocating memory segments and is currently only
+ available on systems that have the <c>mmap</c> system
+ call. Memory segments that are deallocated are kept for a
+ while in a segment cache before they are destroyed. When
+ segments are allocated, cached segments are used if possible
+ instead of creating new segments. This in order to reduce
+ the number of system calls made.</item>
+ </taglist>
+ <p><c>sys_alloc</c> and <c>fix_alloc</c> are always enabled and
+ cannot be disabled. <c>mseg_alloc</c> is always enabled if it is
+ available and an allocator that uses it is enabled. All other
+ allocators can be <seealso marker="#M_e">enabled or disabled</seealso>.
+ By default all allocators are enabled.
+ When an allocator is disabled, <c>sys_alloc</c>
+ is used instead of the disabled allocator.</p>
+ <p>The main idea with the <c>erts_alloc</c> library is to separate
+ memory blocks that are used differently into different memory
+ areas, and by this achieving less memory fragmentation. By
+ putting less effort in finding a good fit for memory blocks that
+ are frequently allocated than for those less frequently
+ allocated, a performance gain can be achieved.</p>
+ </section>
+
+ <section>
+ <marker id="alloc_util"></marker>
+ <title>The alloc_util framework</title>
+ <p>Internally a framework called <c>alloc_util</c> is used for
+ implementing allocators. <c>sys_alloc</c>, <c>fix_alloc</c>, and
+ <c>mseg_alloc</c> do not use this framework; hence, the
+ following does <em>not</em> apply to them.</p>
+ <p>An allocator manages multiple areas, called carriers, in which
+ memory blocks are placed. A carrier is either placed in a
+ separate memory segment (allocated via <c>mseg_alloc</c>) or in
+ the heap segment (allocated via <c>sys_alloc</c>). Multiblock
+ carriers are used for storage of several blocks. Singleblock
+ carriers are used for storage of one block. Blocks that are
+ larger than the value of the singleblock carrier threshold
+ (<seealso marker="#M_sbct">sbct</seealso>) parameter are placed
+ in singleblock carriers. Blocks smaller than the value of the
+ <c>sbct</c> parameter are placed in multiblock
+ carriers. Normally an allocator creates a "main multiblock
+ carrier". Main multiblock carriers are never deallocated. The
+ size of the main multiblock carrier is determined by the value
+ of the <seealso marker="#M_mmbcs">mmbcs</seealso> parameter.</p>
+ <p> <marker id="mseg_mbc_sizes"></marker>
+
+ Sizes of multiblock carriers allocated via <c>mseg_alloc</c> are
+ decided based on the values of the largest multiblock carrier
+ size (<seealso marker="#M_lmbcs">lmbcs</seealso>), the smallest
+ multiblock carrier size (<seealso marker="#M_smbcs">smbcs</seealso>),
+ and the multiblock carrier growth stages
+ (<seealso marker="#M_smbcs">mbcgs</seealso>) parameters. If
+ <c>nc</c> is the current number of multiblock carriers (the main
+ multiblock carrier excluded) managed by an allocator, the size
+ of the next <c>mseg_alloc</c> multiblock carrier allocated by
+ this allocator will roughly be
+ <c><![CDATA[smbcs+nc*(lmbcs-smbcs)/mbcgs]]></c> when
+ <c><![CDATA[nc <= mbcgs]]></c>,
+ and <c>lmbcs</c> when <c><![CDATA[nc > mbcgs]]></c>. If the value of the
+ <c>sbct</c> parameter should be larger than the value of the
+ <c>lmbcs</c> parameter, the allocator may have to create
+ multiblock carriers that are larger than the value of the
+ <c>lmbcs</c> parameter, though. Singleblock carriers allocated
+ via <c>mseg_alloc</c> are sized to whole pages.</p>
+ <p>Sizes of carriers allocated via <c>sys_alloc</c> are
+ decided based on the value of the <c>sys_alloc</c> carrier size
+ (<seealso marker="#Muycs">ycs</seealso>) parameter. The size of
+ a carrier is the least number of multiples of the value of the
+ <c>ycs</c> parameter that satisfies the request.</p>
+ <p>Coalescing of free blocks are always performed immediately.
+ Boundary tags (headers and footers) in free blocks are used
+ which makes the time complexity for coalescing constant.</p>
+ <p> <marker id="strategy"></marker>
+
+ The memory allocation strategy used for multiblock carriers by an
+ allocator is configurable via the <seealso marker="#M_as">as</seealso>
+ parameter. Currently the following strategies are available:</p>
+ <taglist>
+ <tag>Best fit</tag>
+ <item>
+ <p>Strategy: Find the smallest block that satisfies the
+ requested block size.</p>
+ <p>Implementation: A balanced binary search tree is
+ used. The time complexity is proportional to log N, where
+ N is the number of sizes of free blocks.</p>
+ </item>
+ <tag>Address order best fit</tag>
+ <item>
+ <p>Strategy: Find the smallest block that satisfies the
+ requested block size. If multiple blocks are found, choose
+ the one with the lowest address.</p>
+ <p>Implementation: A balanced binary search tree is
+ used. The time complexity is proportional to log N, where
+ N is the number of free blocks.</p>
+ </item>
+ <tag>Good fit</tag>
+ <item>
+ <p>Strategy: Try to find the best fit, but settle for the best fit
+ found during a limited search.</p>
+ <p>Implementation: The implementation uses segregated free
+ lists with a maximum block search depth (in each list) in
+ order to find a good fit fast. When the maximum block
+ search depth is small (by default 3) this implementation
+ has a time complexity that is constant. The maximum block
+ search depth is configurable via the
+ <seealso marker="#M_mbsd">mbsd</seealso> parameter.</p>
+ </item>
+ <tag>A fit</tag>
+ <item>
+ <p>Strategy: Do not search for a fit, inspect only one free
+ block to see if it satisfies the request. This strategy is
+ only intended to be used for temporary allocations.</p>
+ <p>Implementation: Inspect the first block in a free-list.
+ If it satisfies the request, it is used; otherwise, a new
+ carrier is created. The implementation has a time
+ complexity that is constant.</p>
+ <p>As of erts version 5.6.1 the emulator will refuse to
+ use this strategy on other allocators than <c>temp_alloc</c>.
+ This since it will only cause problems for other allocators.</p>
+ </item>
+ </taglist>
+ </section>
+
+ <section>
+ <marker id="flags"></marker>
+ <title>System Flags Effecting erts_alloc</title>
+ <warning>
+ <p>Only use these flags if you are absolutely sure what you are
+ doing. Unsuitable settings may cause serious performance
+ degradation and even a system crash at any time during
+ operation.</p>
+ </warning>
+ <p>Memory allocator system flags have the following syntax:
+ <c><![CDATA[+M<S><P> <V>]]></c>
+ where <c><![CDATA[<S>]]></c> is a letter identifying a subsystem,
+ <c><![CDATA[<P>]]></c> is a parameter, and <c><![CDATA[<V>]]></c> is the
+ value to use. The flags can be passed to the Erlang emulator
+ (<seealso marker="erl">erl</seealso>) as command line
+ arguments.</p>
+ <p>System flags effecting specific allocators have an upper-case
+ letter as <c><![CDATA[<S>]]></c>. The following letters are used for
+ the currently present allocators:</p>
+ <list type="bulleted">
+ <item><c>B: binary_alloc</c></item>
+ <item><c>D: std_alloc</c></item>
+ <item><c>E: ets_alloc</c></item>
+ <item><c>F: fix_alloc</c></item>
+ <item><c>H: eheap_alloc</c></item>
+ <item><c>L: ll_alloc</c></item>
+ <item><c>M: mseg_alloc</c></item>
+ <item><c>R: driver_alloc</c></item>
+ <item><c>S: sl_alloc</c></item>
+ <item><c>T: temp_alloc</c></item>
+ <item><c>Y: sys_alloc</c></item>
+ </list>
+ <p>The following flags are available for configuration of
+ <c>mseg_alloc</c>:</p>
+ <taglist>
+ <tag><c><![CDATA[+MMamcbf <size>]]></c></tag>
+ <item> <marker id="MMamcbf"></marker>
+
+ Absolute max cache bad fit (in kilobytes). A segment in the
+ memory segment cache is not reused if its size exceeds the
+ requested size with more than the value of this
+ parameter. Default value is 4096. </item>
+ <tag><c><![CDATA[+MMrmcbf <ratio>]]></c></tag>
+ <item> <marker id="MMrmcbf"></marker>
+
+ Relative max cache bad fit (in percent). A segment in the
+ memory segment cache is not reused if its size exceeds the
+ requested size with more than relative max cache bad fit
+ percent of the requested size. Default value is 20.</item>
+ <tag><c><![CDATA[+MMmcs <amount>]]></c></tag>
+ <item> <marker id="MMmcs"></marker>
+
+ Max cached segments. The maximum number of memory segments
+ stored in the memory segment cache. Valid range is
+ 0-30. Default value is 5.</item>
+ <tag><c><![CDATA[+MMcci <time>]]></c></tag>
+ <item> <marker id="MMcci"></marker>
+
+ Cache check interval (in milliseconds). The memory segment
+ cache is checked for segments to destroy at an interval
+ determined by this parameter. Default value is 1000.</item>
+ </taglist>
+ <p>The following flags are available for configuration of
+ <c>fix_alloc</c>:</p>
+ <taglist>
+ <tag><c>+MFe true</c></tag>
+ <item> <marker id="MFe"></marker>
+
+ Enable <c>fix_alloc</c>. Note: <c>fix_alloc</c> cannot be disabled.</item>
+ </taglist>
+ <p>The following flags are available for configuration of
+ <c>sys_alloc</c>:</p>
+ <taglist>
+ <tag><c>+MYe true</c></tag>
+ <item> <marker id="MYe"></marker>
+
+ Enable <c>sys_alloc</c>. Note: <c>sys_alloc</c> cannot be disabled.</item>
+ <tag><c>+MYm libc</c></tag>
+ <item> <marker id="MYm"></marker>
+<c>malloc</c> library to use. Currently only
+ <c>libc</c> is available. <c>libc</c> enables the standard
+ <c>libc</c> malloc implementation. By default <c>libc</c> is used.</item>
+ <tag><c><![CDATA[+MYtt <size>]]></c></tag>
+ <item> <marker id="MYtt"></marker>
+
+ Trim threshold size (in kilobytes). This is the maximum amount
+ of free memory at the top of the heap (allocated by
+ <c>sbrk</c>) that will be kept by <c>malloc</c> (not
+ released to the operating system). When the amount of free
+ memory at the top of the heap exceeds the trim threshold,
+ <c>malloc</c> will release it (by calling
+ <c>sbrk</c>). Trim threshold is given in kilobytes. Default
+ trim threshold is 128. <em>Note:</em> This flag will
+ only have any effect when the emulator has been linked with
+ the GNU C library, and uses its <c>malloc</c> implementation.</item>
+ <tag><c><![CDATA[+MYtp <size>]]></c></tag>
+ <item> <marker id="MYtp"></marker>
+
+ Top pad size (in kilobytes). This is the amount of extra
+ memory that will be allocated by <c>malloc</c> when
+ <c>sbrk</c> is called to get more memory from the operating
+ system. Default top pad size is 0. <em>Note:</em> This flag
+ will only have any effect when the emulator has been linked
+ with the GNU C library, and uses its <c>malloc</c>
+ implementation.</item>
+ </taglist>
+ <p>The following flags are available for configuration of allocators
+ based on <c>alloc_util</c>. If <c>u</c> is used as subsystem
+ identifier (i.e., <c><![CDATA[<S> = u]]></c>) all allocators based on
+ <c>alloc_util</c> will be effected. If <c>B</c>, <c>D</c>, <c>E</c>,
+ <c>H</c>, <c>L</c>, <c>R</c>, <c>S</c>, or <c>T</c> is used as
+ subsystem identifier, only the specific allocator identified will be
+ effected:</p>
+ <taglist>
+ <tag><c><![CDATA[+M<S>as bf|aobf|gf|af]]></c></tag>
+ <item> <marker id="M_as"></marker>
+
+ Allocation strategy. Valid strategies are <c>bf</c> (best fit),
+ <c>aobf</c> (address order best fit), <c>gf</c> (good fit),
+ and <c>af</c> (a fit). See
+ <seealso marker="#strategy">the description of allocation strategies</seealso> in "the <c>alloc_util</c> framework" section.</item>
+ <tag><c><![CDATA[+M<S>asbcst <size>]]></c></tag>
+ <item> <marker id="M_asbcst"></marker>
+
+ Absolute singleblock carrier shrink threshold (in
+ kilobytes). When a block located in an
+ <c>mseg_alloc</c> singleblock carrier is shrunk, the carrier
+ will be left unchanged if the amount of unused memory is less
+ than this threshold; otherwise, the carrier will be shrunk.
+ See also <seealso marker="#M_rsbcst">rsbcst</seealso>.</item>
+ <tag><c><![CDATA[+M<S>e true|false]]></c></tag>
+ <item> <marker id="M_e"></marker>
+
+ Enable allocator <c><![CDATA[<S>]]></c>.</item>
+ <tag><c><![CDATA[+M<S>lmbcs <size>]]></c></tag>
+ <item> <marker id="M_lmbcs"></marker>
+
+ Largest (<c>mseg_alloc</c>) multiblock carrier size (in
+ kilobytes). See <seealso marker="#mseg_mbc_sizes">the description
+ on how sizes for mseg_alloc multiblock carriers are decided</seealso>
+ in "the <c>alloc_util</c> framework" section.</item>
+ <tag><c><![CDATA[+M<S>mbcgs <ratio>]]></c></tag>
+ <item> <marker id="M_mbcgs"></marker>
+
+ (<c>mseg_alloc</c>) multiblock carrier growth stages. See
+ <seealso marker="#mseg_mbc_sizes">the description on how sizes for
+ mseg_alloc multiblock carriers are decided</seealso>
+ in "the <c>alloc_util</c> framework" section.</item>
+ <tag><c><![CDATA[+M<S>mbsd <depth>]]></c></tag>
+ <item> <marker id="M_mbsd"></marker>
+
+ Max block search depth. This flag has effect only if the
+ good fit strategy has been selected for allocator
+ <c><![CDATA[<S>]]></c>. When the good fit strategy is used, free
+ blocks are placed in segregated free-lists. Each free list
+ contains blocks of sizes in a specific range. The max block
+ search depth sets a limit on the maximum number of blocks to
+ inspect in a free list during a search for suitable block
+ satisfying the request.</item>
+ <tag><c><![CDATA[+M<S>mmbcs <size>]]></c></tag>
+ <item> <marker id="M_mmbcs"></marker>
+
+ Main multiblock carrier size. Sets the size of the main
+ multiblock carrier for allocator <c><![CDATA[<S>]]></c>. The main
+ multiblock carrier is allocated via <c><![CDATA[sys_alloc]]></c> and is
+ never deallocated.</item>
+ <tag><c><![CDATA[+M<S>mmmbc <amount>]]></c></tag>
+ <item> <marker id="M_mmmbc"></marker>
+
+ Max <c>mseg_alloc</c> multiblock carriers. Maximum number of
+ multiblock carriers allocated via <c>mseg_alloc</c> by
+ allocator <c><![CDATA[<S>]]></c>. When this limit has been reached,
+ new multiblock carriers will be allocated via
+ <c>sys_alloc</c>.</item>
+ <tag><c><![CDATA[+M<S>mmsbc <amount>]]></c></tag>
+ <item> <marker id="M_mmsbc"></marker>
+
+ Max <c>mseg_alloc</c> singleblock carriers. Maximum number of
+ singleblock carriers allocated via <c>mseg_alloc</c> by
+ allocator <c><![CDATA[<S>]]></c>. When this limit has been reached,
+ new singleblock carriers will be allocated via
+ <c>sys_alloc</c>.</item>
+ <tag><c><![CDATA[+M<S>ramv <bool>]]></c></tag>
+ <item> <marker id="M_ramv"></marker>
+
+ Realloc always moves. When enabled, reallocate operations will
+ more or less be translated into an allocate, copy, free sequence.
+ This often reduce memory fragmentation, but costs performance.
+ </item>
+ <tag><c><![CDATA[+M<S>rmbcmt <ratio>]]></c></tag>
+ <item> <marker id="M_rmbcmt"></marker>
+
+ Relative multiblock carrier move threshold (in percent). When
+ a block located in a multiblock carrier is shrunk,
+ the block will be moved if the ratio of the size of the returned
+ memory compared to the previous size is more than this threshold;
+ otherwise, the block will be shrunk at current location.</item>
+ <tag><c><![CDATA[+M<S>rsbcmt <ratio>]]></c></tag>
+ <item> <marker id="M_rsbcmt"></marker>
+
+ Relative singleblock carrier move threshold (in percent). When
+ a block located in a singleblock carrier is shrunk to
+ a size smaller than the value of the
+ <seealso marker="#M_sbct">sbct</seealso> parameter,
+ the block will be left unchanged in the singleblock carrier if
+ the ratio of unused memory is less than this threshold;
+ otherwise, it will be moved into a multiblock carrier. </item>
+ <tag><c><![CDATA[+M<S>rsbcst <ratio>]]></c></tag>
+ <item> <marker id="M_rsbcst"></marker>
+
+ Relative singleblock carrier shrink threshold (in
+ percent). When a block located in an <c>mseg_alloc</c>
+ singleblock carrier is shrunk, the carrier will be left
+ unchanged if the ratio of unused memory is less than this
+ threshold; otherwise, the carrier will be shrunk.
+ See also <seealso marker="#M_asbcst">asbcst</seealso>.</item>
+ <tag><c><![CDATA[+M<S>sbct <size>]]></c></tag>
+ <item> <marker id="M_sbct"></marker>
+
+ Singleblock carrier threshold. Blocks larger than this
+ threshold will be placed in singleblock carriers. Blocks
+ smaller than this threshold will be placed in multiblock
+ carriers.</item>
+ <tag><c><![CDATA[+M<S>smbcs <size>]]></c></tag>
+ <item> <marker id="M_smbcs"></marker>
+
+ Smallest (<c>mseg_alloc</c>) multiblock carrier size (in
+ kilobytes). See <seealso marker="#mseg_mbc_sizes">the description
+ on how sizes for mseg_alloc multiblock carriers are decided</seealso>
+ in "the <c>alloc_util</c> framework" section.</item>
+ <tag><c><![CDATA[+M<S>t true|false|<amount>]]></c></tag>
+ <item> <marker id="M_t"></marker>
+
+ Multiple, thread specific instances of the allocator.
+ This option will only have any effect on the runtime system
+ with SMP support. Default behaviour on the runtime system with
+ SMP support (<c>N</c> equals the number of scheduler threads):
+ <taglist>
+ <tag><c>temp_alloc</c></tag>
+ <item><c>N + 1</c> instances.</item>
+ <tag><c>ll_alloc</c></tag>
+ <item><c>1</c> instance.</item>
+ <tag>Other allocators</tag>
+ <item><c>N</c> instances when <c>N</c> is less than or equal to
+ <c>16</c>. <c>16</c> instances when <c>N</c> is greater than
+ <c>16</c>.</item>
+ </taglist>
+ <c>temp_alloc</c> will always use <c>N + 1</c> instances when
+ this option has been enabled regardless of the amount passed.
+ Other allocators will use the same amount of instances as the
+ amount passed as long as it isn't greater than <c>N</c>.
+ </item>
+ </taglist>
+ <p>Currently the following flags are available for configuration of
+ <c>alloc_util</c>, i.e. all allocators based on <c>alloc_util</c>
+ will be effected:</p>
+ <taglist>
+ <tag><c><![CDATA[+Muycs <size>]]></c></tag>
+ <item> <marker id="Muycs"></marker>
+<c>sys_alloc</c> carrier size. Carriers allocated via
+ <c>sys_alloc</c> will be allocated in sizes which are
+ multiples of the <c>sys_alloc</c> carrier size. This is not
+ true for main multiblock carriers and carriers allocated
+ during a memory shortage, though.</item>
+ <tag><c><![CDATA[+Mummc <amount>]]></c></tag>
+ <item> <marker id="Mummc"></marker>
+
+ Max <c>mseg_alloc</c> carriers. Maximum number of carriers
+ placed in separate memory segments. When this limit has been
+ reached, new carriers will be placed in memory retrieved from
+ <c>sys_alloc</c>.</item>
+ </taglist>
+ <p>Instrumentation flags:</p>
+ <taglist>
+ <tag><c>+Mim true|false</c></tag>
+ <item> <marker id="Mim"></marker>
+
+ A map over current allocations is kept by the emulator. The
+ allocation map can be retrieved via the <c>instrument</c>
+ module. <c>+Mim true</c> implies <c>+Mis true</c>.
+ <c>+Mim true</c> is the same as
+ <seealso marker="erl#instr">-instr</seealso>.</item>
+ <tag><c>+Mis true|false</c></tag>
+ <item> <marker id="Mis"></marker>
+
+ Status over allocated memory is kept by the emulator. The
+ allocation status can be retrieved via the <c>instrument</c>
+ module.</item>
+ <tag><c>+Mit X</c></tag>
+ <item> <marker id="Mit"></marker>
+
+ Reserved for future use. Do <em>not</em> use this flag.</item>
+ </taglist>
+ <note>
+ <p>When instrumentation of the emulator is enabled, the emulator
+ uses more memory and runs slower.</p>
+ </note>
+ <p>Other flags:</p>
+ <taglist>
+ <tag><c>+Mea min|max|r9c|r10b|r11b|config</c></tag>
+ <item> <marker id="Mea"></marker>
+ <taglist>
+ <tag><c>min</c></tag>
+ <item>
+ Disables all allocators that can be disabled.
+ </item>
+
+ <tag><c>max</c></tag>
+ <item>
+ Enables all allocators (currently default).
+ </item>
+
+ <tag><c>r9c|r10b|r11b</c></tag>
+ <item>
+ Configures all allocators as they were configured in respective
+ OTP release. These will eventually be removed.
+ </item>
+
+ <tag><c>config</c></tag>
+ <item>
+ Disables features that cannot be enabled while creating an
+ allocator configuration with
+ <seealso marker="runtime_tools:erts_alloc_config">erts_alloc_config(3)</seealso>.
+ Note, this option should only be used while running
+ <c>erts_alloc_config</c>, <em>not</em> when using the created
+ configuration.
+ </item>
+ </taglist>
+ </item>
+ </taglist>
+ <p>Only some default values have been presented
+ here.
+ <seealso marker="erts:erlang#system_info_allocator">erlang:system_info(allocator)</seealso>,
+ and
+ <seealso marker="erts:erlang#system_info_allocator_tuple">erlang:system_info({allocator, Alloc})</seealso>
+ can be used in order to obtain currently used settings and current
+ status of the allocators.</p>
+ <note>
+ <p>Most of these flags are highly implementation dependent, and they
+ may be changed or removed without prior notice.</p>
+ <p><c>erts_alloc</c> is not obliged to strictly use the settings that
+ have been passed to it (it may even ignore them).</p>
+ </note>
+ <p><seealso marker="runtime_tools:erts_alloc_config">erts_alloc_config(3)</seealso>
+ is a tool that can be used to aid creation of an
+ <c>erts_alloc</c> configuration that is suitable for a limited
+ number of runtime scenarios.</p>
+ </section>
+
+ <section>
+ <title>SEE ALSO</title>
+ <p><seealso marker="runtime_tools:erts_alloc_config">erts_alloc_config(3)</seealso>,
+ <seealso marker="erl">erl(1)</seealso>,
+ <seealso marker="tools:instrument">instrument(3)</seealso>,
+ <seealso marker="erts:erlang">erlang(3)</seealso></p>
+ </section>
+</cref>
+