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-rw-r--r--erts/doc/src/erts_alloc.xml86
1 files changed, 47 insertions, 39 deletions
diff --git a/erts/doc/src/erts_alloc.xml b/erts/doc/src/erts_alloc.xml
index c73cdfd290..2ffb55c6ab 100644
--- a/erts/doc/src/erts_alloc.xml
+++ b/erts/doc/src/erts_alloc.xml
@@ -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 +170,15 @@
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 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 +215,6 @@
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 +236,6 @@
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>
@@ -319,10 +309,42 @@
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. Currently the default
+ is zero. 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. 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 <c>aoff</c> and the <c>aoffcaobf</c> strategies 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
+ 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>
<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>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 +438,6 @@
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