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authorRickard Green <[email protected]>2011-11-13 21:41:11 +0100
committerRickard Green <[email protected]>2011-11-13 21:41:11 +0100
commitc12befbdc957f7f166598c6d5143ce27a0d10fa8 (patch)
treebb2077e2d28f1432ea3dc9f2da971d0ca5634e94 /erts/doc/src
parent4ed347dcaeeb8e8844be532414a11817da3920f5 (diff)
parenta67e91e658bdbba24fcc3c79b06fdf10ff830bc9 (diff)
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Merge branch 'rickard/alloc-opt/OTP-7775'
* rickard/alloc-opt/OTP-7775: Optimize memory allocation Conflicts: erts/aclocal.m4 erts/emulator/hipe/hipe_bif_list.m4 erts/preloaded/ebin/erl_prim_loader.beam erts/preloaded/ebin/erlang.beam erts/preloaded/ebin/init.beam erts/preloaded/ebin/otp_ring0.beam erts/preloaded/ebin/prim_file.beam erts/preloaded/ebin/prim_inet.beam erts/preloaded/ebin/prim_zip.beam erts/preloaded/ebin/zlib.beam
Diffstat (limited to 'erts/doc/src')
-rw-r--r--erts/doc/src/erts_alloc.xml58
1 files changed, 24 insertions, 34 deletions
diff --git a/erts/doc/src/erts_alloc.xml b/erts/doc/src/erts_alloc.xml
index 86e1e5168a..3b5ee5391c 100644
--- a/erts/doc/src/erts_alloc.xml
+++ b/erts/doc/src/erts_alloc.xml
@@ -58,11 +58,8 @@
<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>
+ <item>A fast allocator used for some frequently used
+ fixed size data types.</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>
@@ -83,7 +80,7 @@
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
+ <p><c>sys_alloc</c> is 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>.
@@ -104,7 +101,7 @@
<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
+ implementing allocators. <c>sys_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
@@ -212,6 +209,14 @@
This since it will only cause problems for other allocators.</p>
</item>
</taglist>
+ <p>Apart from the ordinary allocators described above a number of
+ pre-allocators are used for some specific data types. These
+ pre-allocators pre-allocate a fixed amount of memory for certain data
+ types when the run-time system starts. As long as there are available
+ pre-allocated memory, it will be used. When no pre-allocated memory is
+ available, memory will be allocated in ordinary allocators. These
+ pre-allocators are typically much faster than the ordinary allocators,
+ but can only satisfy a limited amount of requests.</p>
</section>
<note><p>
@@ -272,18 +277,6 @@
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><marker id="MMcci"><c><![CDATA[+MMcci <time>]]></c></marker></tag>
- <item>
- 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><marker id="MFe"><c>+MFe true</c></marker></tag>
- <item>
- 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>
@@ -322,7 +315,7 @@
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
+ <c>F</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>
@@ -441,26 +434,23 @@
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><marker id="M_t"><c><![CDATA[+M<S>t true|false|<amount>]]></c></marker></tag>
+ <tag><marker id="M_t"><c><![CDATA[+M<S>t true|false]]></c></marker></tag>
<item>
- <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 (<c>N</c> equals the number of scheduler threads):</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:
<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>
+ <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>
- <p><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>.</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.
</item>
</taglist>
<p>Currently the following flags are available for configuration of