diff options
Diffstat (limited to 'erts/doc/src/erts_alloc.xml')
| -rw-r--r-- | erts/doc/src/erts_alloc.xml | 199 |
1 files changed, 149 insertions, 50 deletions
diff --git a/erts/doc/src/erts_alloc.xml b/erts/doc/src/erts_alloc.xml index c73cdfd290..1ade41f1aa 100644 --- a/erts/doc/src/erts_alloc.xml +++ b/erts/doc/src/erts_alloc.xml @@ -1,10 +1,10 @@ -<?xml version="1.0" encoding="latin1" ?> +<?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE cref SYSTEM "cref.dtd"> <cref> <header> <copyright> - <year>2002</year><year>2013</year> + <year>2002</year><year>2014</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -75,10 +75,6 @@ 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> - <tag><c>sbmbc_alloc</c></tag> - <item>Allocator used by other allocators for allocation of carriers - where only small blocks are placed. Currently this allocator is - disabled by default.</item> </taglist> <p><c>sys_alloc</c> is always enabled and cannot be disabled. <c>mseg_alloc</c> is always enabled if it is @@ -86,9 +82,7 @@ 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. <c>sbmbc_alloc</c> is an exception. If - <c>sbmbc_alloc</c> is disabled, other allocators will not handle - small blocks in separate carriers.</p> + 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 @@ -106,20 +100,15 @@ 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>), in - the heap segment (allocated via <c>sys_alloc</c>), or inside - another carrier (in case it is a carrier created by - <c>sbmbc_alloc</c>). Multiblock + 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 that are smaller than the value of the <c>sbct</c> parameter are placed in multiblock - carriers. Blocks that are smaller than the small block multiblock - carrier threshold (<seealso marker="#M_sbmbct">sbmbct</seealso>) - will be placed in multiblock carriers only used for small blocks. - Normally an allocator creates a "main 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> @@ -140,9 +129,7 @@ <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. The size of multiblock carriers - for small blocks is determined by the small block multiblock - carrier size (<seealso marker="#M_sbmbcs">sbmbcs</seealso>). + <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 @@ -183,6 +170,24 @@ used. The time complexity is proportional to log N, where N is the number of free blocks.</p> </item> + <tag>Address order first fit carrier best fit</tag> + <item> + <p>Strategy: Find the <em>carrier</em> with the lowest address that + can satisfy the requested block size, then find a block within + that carrier using the "best fit" strategy.</p> + <p>Implementation: Balanced binary search trees are + used. The time complexity is proportional to log N, where + N is the number of free blocks.</p> + </item> + <tag>Address order first fit carrier address order best fit</tag> + <item> + <p>Strategy: Find the <em>carrier</em> with the lowest address that + can satisfy the requested block size, then find a block within + that carrier using the "adress order best fit" strategy.</p> + <p>Implementation: Balanced binary search trees are + 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 @@ -219,11 +224,6 @@ but can only satisfy a limited amount of requests.</p> </section> - <note><p> - Currently only allocators using the best fit and the address order - best fit strategies are able to use "small block multi block carriers". - </p></note> - <section> <marker id="flags"></marker> <title>System Flags Effecting erts_alloc</title> @@ -245,7 +245,6 @@ the currently present allocators:</p> <list type="bulleted"> <item><c>B: binary_alloc</c></item> - <item><c>C: sbmbc_alloc</c></item> <item><c>D: std_alloc</c></item> <item><c>E: ets_alloc</c></item> <item><c>F: fix_alloc</c></item> @@ -272,6 +271,77 @@ 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><marker id="MMsco"><c><![CDATA[+MMsco true|false]]></c></marker></tag> + <item> + Set <seealso marker="#MMscs">super carrier</seealso> only flag. This + flag defaults to <c>true</c>. When a super carrier is used and this + flag is <c>true</c>, <c>mseg_alloc</c> will only create carriers + in the super carrier. Note that the <c>alloc_util</c> framework may + create <c>sys_alloc</c> carriers, so if you want all carriers to + be created in the super carrier, you therefore want to disable use + of <c>sys_alloc</c> carriers by also passing + <seealso marker="#Musac"><c>+Musac false</c></seealso>. When the flag + is <c>false</c>, <c>mseg_alloc</c> will try to create carriers outside + of the super carrier when the super carrier is full. + <br/><br/> + <em>NOTE</em>: Setting this flag to <c>false</c> may not be supported + on all systems. This flag will in that case be ignored. + <br/><br/> + <em>NOTE</em>: The super carrier cannot be enabled nor + disabled on halfword heap systems. This flag will be + ignored on halfword heap systems. + </item> + <tag><marker id="MMscrfsd"><c><![CDATA[+MMscrfsd <amount>]]></c></marker></tag> + <item> + Set <seealso marker="#MMscs">super carrier</seealso> reserved + free segment descriptors. This parameter defaults to <c>65536</c>. + This parameter determines the amount of memory to reserve for + free segment descriptors used by the super carrier. If the system + runs out of reserved memory for free segment descriptors, other + memory will be used. This may however cause fragmentation issues, + so you want to ensure that this never happens. The maximum amount + of free segment descriptors used can be retrieved from the + <c>erts_mmap</c> tuple part of the result from calling + <seealso marker="erts:erlang#system_info_allocator_tuple">erlang:system_info({allocator, mseg_alloc})</seealso>. + </item> + <tag><marker id="MMscrpm"><c><![CDATA[+MMscrpm true|false]]></c></marker></tag> + <item> + Set <seealso marker="#MMscs">super carrier</seealso> reserve physical + memory flag. This flag defaults to <c>true</c>. When this flag is + <c>true</c>, physical memory will be reserved for the whole super + carrier at once when it is created. The reservation will after that + be left unchanged. When this flag is set to <c>false</c> only virtual + address space will be reserved for the super carrier upon creation. + The system will attempt to reserve physical memory upon carrier + creations in the super carrier, and attempt to unreserve physical + memory upon carrier destructions in the super carrier. + <br/><br/> + <em>NOTE</em>: What reservation of physical memory actually means + highly depends on the operating system, and how it is configured. For + example, different memory overcommit settings on Linux drastically + change the behaviour. Also note, setting this flag to <c>false</c> + may not be supported on all systems. This flag will in that case + be ignored. + <br/><br/> + <em>NOTE</em>: The super carrier cannot be enabled nor + disabled on halfword heap systems. This flag will be + ignored on halfword heap systems. + </item> + <tag><marker id="MMscs"><c><![CDATA[+MMscs <size in MB>]]></c></marker></tag> + <item> + Set super carrier size (in MB). The super carrier size defaults to + zero; i.e, the super carrier is by default disabled. The super + carrier is a large continuous area in the virtual address space. + <c>mseg_alloc</c> will always try to create new carriers in the super + carrier if it exists. Note that the <c>alloc_util</c> framework may + create <c>sys_alloc</c> carriers. For more information on this, see the + documentation of the <seealso marker="#MMsco"><c>+MMsco</c></seealso> + flag. + <br/><br/> + <em>NOTE</em>: The super carrier cannot be enabled nor + disabled on halfword heap systems. This flag will be + ignored on halfword heap systems. + </item> <tag><marker id="MMmcs"><c><![CDATA[+MMmcs <amount>]]></c></marker></tag> <item> Max cached segments. The maximum number of memory segments @@ -319,10 +389,44 @@ subsystem identifier, only the specific allocator identified will be effected:</p> <taglist> - <tag><marker id="M_as"><c><![CDATA[+M<S>as bf|aobf|aoff|gf|af]]></c></marker></tag> + <tag><marker id="M_acul"><c><![CDATA[+M<S>acul <utilization>|de]]></c></marker></tag> + <item> + Abandon carrier utilization limit. A valid + <c><![CDATA[<utilization>]]></c> is an integer in the range + <c>[0, 100]</c> representing utilization in percent. When a + utilization value larger than zero is used, allocator instances + are allowed to abandon multiblock carriers. If <c>de</c> (default + enabled) is passed instead of a <c><![CDATA[<utilization>]]></c>, + a recomended non zero utilization value will be used. The actual + value chosen depend on allocator type and may be changed between + ERTS versions. Currently the default equals <c>de</c>, but this + may be changed in the future. Carriers will be abandoned when + memory utilization in the allocator instance falls below the + utilization value used. Once a carrier has been abandoned, no new + allocations will be made in it. When an allocator instance gets an + increased multiblock carrier need, it will first try to fetch an + abandoned carrier from an allocator instances of the same + allocator type. If no abandoned carrier could be fetched, it will + create a new empty carrier. When an abandoned carrier has been + fetched it will function as an ordinary carrier. This feature has + special requirements on the + <seealso marker="#M_as">allocation strategy</seealso> used. Currently + only the strategies <c>aoff</c>, <c>aoffcbf</c> and <c>aoffcaobf</c> support + abandoned carriers. This feature also requires + <seealso marker="#M_t">multiple thread specific instances</seealso> + to be enabled. When enabling this feature, multiple thread specific + instances will be enabled if not already enabled, and the + <c>aoffcbf</c> strategy will be enabled if current strategy does not + support abandoned carriers. This feature can be enabled on all + allocators based on the <c>alloc_util</c> framework with the + exception of <c>temp_alloc</c> (which would be pointless). + </item> + <tag><marker id="M_as"><c><![CDATA[+M<S>as bf|aobf|aoff|aoffcbf|aoffcaobf|gf|af]]></c></marker></tag> <item> Allocation strategy. Valid strategies are <c>bf</c> (best fit), <c>aobf</c> (address order best fit), <c>aoff</c> (address order first fit), + <c>aoffcbf</c> (address order first fit carrier best fit), + <c>aoffcaobf</c> (address order first fit carrier 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><marker id="M_asbcst"><c><![CDATA[+M<S>asbcst <size>]]></c></marker></tag> @@ -416,20 +520,6 @@ smaller than this threshold will be placed in multiblock carriers. On 32-bit Unix style OS this threshold can not be set higher than 8 megabytes.</item> - <tag><marker id="M_sbmbcs"><c><![CDATA[+M<S>sbmbcs <size>]]></c></marker></tag> - <item> - Small block multiblock carrier size (in bytes). Memory blocks smaller - than the small block multiblock carrier threshold - (<seealso marker="#M_sbmbct">sbmbct</seealso>) will be placed in - multiblock carriers used for small blocks only. This parameter - determines the size of such carriers. - </item> - <tag><marker id="M_sbmbct"><c><![CDATA[+M<S>sbmbct <size>]]></c></marker></tag> - <item> - Small block multiblock carrier threshold (in bytes). Memory blocks - smaller than this threshold will be placed in multiblock carriers - used for small blocks only. - </item> <tag><marker id="M_smbcs"><c><![CDATA[+M<S>smbcs <size>]]></c></marker></tag> <item> Smallest (<c>mseg_alloc</c>) multiblock carrier size (in @@ -441,15 +531,9 @@ <p>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:</p> - <taglist> - <tag><c>ll_alloc</c></tag> - <item><c>1</c> instance.</item> - <tag>Other allocators</tag> - <item><c>NoSchedulers+1</c> instances. Each scheduler will use - a lock-free instance of its own and other threads will use - a common instance.</item> - </taglist> + SMP support is <c>NoSchedulers+1</c> instances. Each scheduler will use + a lock-free instance of its own and other threads will use + a common instance.</p> <p>It was previously (before ERTS version 5.9) possible to configure a smaller amount of thread specific instances than schedulers. This is, however, not possible any more.</p> @@ -472,6 +556,11 @@ 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> + <tag><marker id="Musac"><c><![CDATA[+Musac <bool>]]></c></marker></tag> + <item> + Allow <c>sys_alloc</c> carriers. By default <c>true</c>. If + set to <c>false</c>, <c>sys_alloc</c> carriers will never be + created by allocators using the <c>alloc_util</c> framework.</item> </taglist> <p>Instrumentation flags:</p> <taglist> @@ -527,6 +616,16 @@ </item> </taglist> </item> + <tag><marker id="Mlpm"><c>+Mlpm all|no</c></marker></tag> + <item>Lock physical memory. The default value is <c>no</c>, i.e., + no physical memory will be locked. If set to <c>all</c>, all + memory mappings made by the runtime system, will be locked into + physical memory. If set to <c>all</c>, the runtime system will fail + to start if this feature is not supported, the user has not got enough + privileges, or the user is not allowed to lock enough physical memory. + The runtime system will also fail with an out of memory condition + if the user limit on the amount of locked memory is reached. + </item> </taglist> <p>Only some default values have been presented here. |