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authorErlang/OTP <[email protected]>2011-07-11 15:40:42 +0200
committerErlang/OTP <[email protected]>2011-07-11 15:40:42 +0200
commit3b2f96b9a1f079c9e0502db7d11984597ea5c4f1 (patch)
treeeb14eeaeda15e219244540f0d270f212a5dc9554 /erts/doc
parente0f60ce445b072b97353f3ab8f18c2f00b04cbe8 (diff)
parent1dfaae304dfcc4f249c62b5ab7ff3bd4acef0d50 (diff)
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Merge branch 'rickard/sbmbc/OTP-9339' into maint-r14
* rickard/sbmbc/OTP-9339: Use separate memory carriers for small blocks
Diffstat (limited to 'erts/doc')
-rw-r--r--erts/doc/src/erts_alloc.xml52
1 files changed, 43 insertions, 9 deletions
diff --git a/erts/doc/src/erts_alloc.xml b/erts/doc/src/erts_alloc.xml
index 51a4a2bca0..452e5d990e 100644
--- a/erts/doc/src/erts_alloc.xml
+++ b/erts/doc/src/erts_alloc.xml
@@ -78,14 +78,20 @@
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> 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>
+ 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>
<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
@@ -103,15 +109,20 @@
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
+ 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
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
+ 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
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>
@@ -133,8 +144,11 @@
<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>
+ <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>).
+ 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
@@ -194,6 +208,11 @@
</taglist>
</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>
@@ -215,6 +234,7 @@
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>
@@ -395,6 +415,20 @@
threshold will be placed in singleblock carriers. Blocks
smaller than this threshold will be placed in multiblock
carriers.</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