diff options
Diffstat (limited to 'erts/doc/src/erts_alloc.xml')
| -rw-r--r-- | erts/doc/src/erts_alloc.xml | 102 |
1 files changed, 99 insertions, 3 deletions
diff --git a/erts/doc/src/erts_alloc.xml b/erts/doc/src/erts_alloc.xml index 9ea2e7a6b5..c9eca39a99 100644 --- a/erts/doc/src/erts_alloc.xml +++ b/erts/doc/src/erts_alloc.xml @@ -170,6 +170,15 @@ 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 @@ -262,6 +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 @@ -331,20 +411,21 @@ 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 <c>aoff</c> and the <c>aoffcaobf</c> strategies support + 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>aoffcaobf</c> strategy will be enabled if current strategy does not + <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|aoffcaobf|gf|af]]></c></marker></tag> + <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> @@ -481,6 +562,11 @@ 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> @@ -536,6 +622,16 @@ </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. |