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<img alt="Erlang logo" src="../../../../doc/erlang-logo.png"><br><small><a href="users_guide.html">User's Guide</a><br><a href="index.html">Reference Manual</a><br><a href="release_notes.html">Release Notes</a><br><a href="../pdf/tools-2.6.8.pdf">PDF</a><br><a href="../../../../doc/index.html">Top</a></small><p><strong>Tools</strong><br><strong>Reference Manual</strong><br><small>Version 2.6.8</small></p>
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<!-- refpage --><center><h1>instrument</h1></center>
<h3>MODULE</h3>
<div class="REFBODY">instrument</div>
<h3>MODULE SUMMARY</h3>
<div class="REFBODY">Analysis and Utility Functions for Instrumentation</div>
<h3>DESCRIPTION</h3>
<div class="REFBODY"><p>
<p>The module <span class="code">instrument</span> contains support for studying the resource
usage in an Erlang runtime system. Currently, only the allocation of memory can
be studied.</p>
<div class="note">
<div class="label">Note</div>
<div class="content"><p>
<p>Note that this whole module is experimental, and the representations
used as well as the functionality is likely to change in the future.</p>
<p>The <span class="code">instrument</span> module interface was slightly changed in
Erlang/OTP R9C.</p>
</p></div>
</div>
<p>To start an Erlang runtime system with instrumentation, use the
<span class="code">+Mi*</span> set of command-line arguments to the <span class="code">erl</span> command (see
the erts_alloc(3) and erl(1) man pages).</p>
<p>The basic object of study in the case of memory allocation is a memory
allocation map. A memory allocation map contains a list of descriptors
for each allocated memory block. Currently, a descriptor is a 4-tuple</p>
<div class="example"><pre>
{TypeNo, Address, Size, PidDesc} </pre></div>
<p>where <span class="code">TypeNo</span> is the memory block type number, <span class="code">Address</span>
is its place in memory, and <span class="code">Size</span> is its size, in bytes.
<span class="code">PidDesc</span> is either a tuple <span class="code">{X,Y,Z}</span> identifying the
process which was executing when the block was allocated, or
<span class="code">undefined</span> if no process was executing. The pid tuple
<span class="code">{X,Y,Z}</span> can be transformed into a real pid by usage of the
<span class="code">c:pid/3</span> function.</p>
<p>Various details about memory allocation:</p>
<p>Memory blocks are allocated both on the heap segment and on other memory
segments. This can cause the instrumentation functionality to report
very large holes. Currently the instrumentation functionality doesn't
provide any support for distinguishing between holes between memory
segments, and holes between allocated blocks inside memory segments.
The current size of the process cannot be obtained from within Erlang,
but can be seen with one of the system statistics tools, e.g.,
<span class="code">ps</span> or <span class="code">top</span>. The Solaris utility <span class="code">pmap</span> can be
useful. It reports currently mapped memory segments. </p>
<p>Overhead for instrumentation: When the emulator has been started with
the <span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','erts','erts_alloc.html#Mim');">"+Mim true"</a></span>
flag, each block is preceded by a 24 bytes large
header on a 32-bit machine and a 48 bytes large header on a 64-bit
machine. When the emulator has been started with the
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','erts','erts_alloc.html#Mis');">"+Mis true"</a></span>
flag, each block is preceded by an 8 bytes large header. These are the header
sizes used by the Erlang 5.3/OTP R9C emulator. Other versions of the
emulator may use other header sizes. The function
<span class="bold_code"><a href="#block_header_size-1">block_header_size/1</a></span>
can be used for retrieving the header size used for a specific memory
allocation map. The time overhead for managing the instrumentation
data is small.</p>
<p>Sizes presented by the instrumentation functionality are (by the
emulator) requested sizes, i.e. neither instrumentation headers nor
headers used by allocators are included.</p>
</p></div>
<h3>EXPORTS</h3>
<p><a name="allocator_descr-2"><span class="bold_code">allocator_descr(MemoryData, TypeNo) -> AllocDescr | invalid_type | "unknown"</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">TypeNo = int()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocDescr = atom() | string()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Returns the allocator description of the allocator that
manages memory blocks of type number <span class="code">TypeNo</span> used in
<span class="code">MemoryData</span>.
Valid <span class="code">TypeNo</span>s are in the range returned by
<span class="bold_code"><a href="#type_no_range-1">type_no_range/1</a></span> on
this specific memory allocation map. If <span class="code">TypeNo</span> is an
invalid integer, <span class="code">invalid_type</span> is returned.</p>
</p></div>
<p><a name="block_header_size-1"><span class="bold_code">block_header_size(MemoryData) -> int()</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
</div>
<div class="REFBODY"><p>
<a name="block_header_size_1"></a>
<p>Returns the memory block header size used by the
emulator that generated the memory allocation map. The block
header size may differ between different emulators.</p>
</p></div>
<p><a name="class_descr-2"><span class="bold_code">class_descr(MemoryData, TypeNo) -> ClassDescr | invalid_type | "unknown"</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">TypeNo = int()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">ClassDescr = atom() | string()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Returns the class description of the class that
the type number <span class="code">TypeNo</span> used in <span class="code">MemoryData</span> belongs
to.
Valid <span class="code">TypeNo</span>s are in the range returned by
<span class="bold_code"><a href="#type_no_range-1">type_no_range/1</a></span> on
this specific memory allocation map. If <span class="code">TypeNo</span> is an
invalid integer, <span class="code">invalid_type</span> is returned.</p>
</p></div>
<p><a name="descr-1"><span class="bold_code">descr(MemoryData) -> DescrMemoryData</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">DescrMemoryData = {term(), DescrAllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">DescrAllocList = [DescrDesc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">DescrDesc = {TypeDescr, int(), int(), DescrPidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">TypeDescr = atom() | string()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">DescrPidDesc = pid() | undefined</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Returns a memory allocation map where the type numbers (first
element of <span class="code">Desc</span>) have been replaced by type descriptions,
and pid tuples (fourth element of <span class="code">Desc</span>) have been
replaced by real pids.</p>
</p></div>
<p><a name="holes-1"><span class="bold_code">holes(MemoryData) -> ok</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Prints out the size of each hole (i.e., the space between
allocated blocks) on the terminal. <strong>NOTE:</strong> Really large holes
are probably holes between memory segments.
The memory allocation map has to be sorted (see
<span class="bold_code"><a href="#sort-1">sort/1</a></span>).</p>
</p></div>
<p><a name="mem_limits-1"><span class="bold_code">mem_limits(MemoryData) -> {Low, High}</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Low = High = int()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Returns a tuple <span class="code">{Low, High}</span> indicating
the lowest and highest address used.
The memory allocation map has to be sorted (see
<span class="bold_code"><a href="#sort-1">sort/1</a></span>).</p>
</p></div>
<p><a name="memory_data-0"><span class="bold_code">memory_data() -> MemoryData | false</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Returns <span class="code">MemoryData</span> (a the memory allocation map)
if the emulator has been started with the "<span class="code">+Mim true</span>"
command-line argument; otherwise, <span class="code">false</span>. <strong>NOTE:</strong><span class="code">memory_data/0</span> blocks execution of other processes while
the data is collected. The time it takes to collect the data can
be substantial.</p>
</p></div>
<p><a name="memory_status-1"><span class="bold_code">memory_status(StatusType) -> [StatusInfo] | false</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">StatusType = total | allocators | classes | types</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">StatusInfo = {About, [Info]}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">About = atom()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Info = {InfoName, Current, MaxSinceLast, MaxEver}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">InfoName = sizes|blocks</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Current = int()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">MaxSinceLast = int()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">MaxEver = int()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Returns a list of <span class="code">StatusInfo</span> if the emulator has been
started with the "<span class="code">+Mis true</span>" or "<span class="code">+Mim true</span>"
command-line argument; otherwise, <span class="code">false</span>. </p>
<p>See the
<span class="bold_code"><a href="#read_memory_status-1">read_memory_status/1</a></span>
function for a description of the <span class="code">StatusInfo</span> term.</p>
</p></div>
<p><a name="read_memory_data-1"><span class="bold_code">read_memory_data(File) -> MemoryData | {error, Reason}</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">File = string()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
</div>
<div class="REFBODY"><p>
<a name="read_memory_data_1"></a>
<p>Reads a memory allocation map from the file <span class="code">File</span> and
returns it. The file is assumed to have been created by
<span class="code">store_memory_data/1</span>. The error codes are the same as for
<span class="code">file:consult/1</span>.</p>
</p></div>
<p><a name="read_memory_status-1"><span class="bold_code">read_memory_status(File) -> MemoryStatus | {error, Reason}</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">File = string()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">MemoryStatus = [{StatusType, [StatusInfo]}]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">StatusType = total | allocators | classes | types</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">StatusInfo = {About, [Info]}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">About = atom()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Info = {InfoName, Current, MaxSinceLast, MaxEver}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">InfoName = sizes|blocks</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Current = int()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">MaxSinceLast = int()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">MaxEver = int()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<a name="read_memory_status_1"></a>
<p>Reads memory allocation status from the file <span class="code">File</span> and
returns it. The file is assumed to have been created by
<span class="code">store_memory_status/1</span>. The error codes are the same as
for <span class="code">file:consult/1</span>.</p>
<p>When <span class="code">StatusType</span> is <span class="code">allocators</span>, <span class="code">About</span> is
the allocator that the information is about. When
<span class="code">StatusType</span> is <span class="code">types</span>, <span class="code">About</span> is
the memory block type that the information is about. Memory
block types are not described other than by their name and may
vary between emulators. When <span class="code">StatusType</span> is <span class="code">classes</span>,
<span class="code">About</span> is the memory block type class that information is
presented about. Memory block types are classified after their
use. Currently the following classes exist:</p>
<dl>
<dt><strong><span class="code">process_data</span></strong></dt>
<dd>Erlang process specific data.</dd>
<dt><strong><span class="code">binary_data</span></strong></dt>
<dd>Erlang binaries.</dd>
<dt><strong><span class="code">atom_data</span></strong></dt>
<dd>Erlang atoms.</dd>
<dt><strong><span class="code">code_data</span></strong></dt>
<dd>Erlang code.</dd>
<dt><strong><span class="code">system_data</span></strong></dt>
<dd>Other data used by the system</dd>
</dl>
<p>When <span class="code">InfoName</span> is <span class="code">sizes</span>, <span class="code">Current</span>,
<span class="code">MaxSinceLast</span>, and <span class="code">MaxEver</span> are, respectively, current
size, maximum size since last call to
<span class="code">store_memory_status/1</span> or <span class="code">memory_status/1</span> with the
specific <span class="code">StatusType</span>, and maximum size since the emulator
was started. When <span class="code">InfoName</span> is <span class="code">blocks</span>, <span class="code">Current</span>,
<span class="code">MaxSinceLast</span>, and <span class="code">MaxEver</span> are, respectively, current
number of blocks, maximum number of blocks since last call to
<span class="code">store_memory_status/1</span> or <span class="code">memory_status/1</span> with the
specific <span class="code">StatusType</span>, and maximum number of blocks since the
emulator was started. </p>
<p><strong>NOTE:</strong>A memory block is accounted for at
"the first level" allocator. E.g. <span class="code">fix_alloc</span> allocates its
memory pools via <span class="code">ll_alloc</span>. When a <span class="code">fix_alloc</span> block
is allocated, neither the block nor the pool in which it resides
are accounted for as memory allocated via <span class="code">ll_alloc</span> even
though it is.</p>
</p></div>
<p><a name="sort-1"><span class="bold_code">sort(MemoryData) -> MemoryData</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
</div>
<div class="REFBODY"><p>
<a name="sort_1"></a>
<p>Sorts a memory allocation map so that the addresses are in
ascending order.</p>
</p></div>
<p><a name="store_memory_data-1"><span class="bold_code">store_memory_data(File) -> true|false</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">File = string()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Stores the current memory allocation map on the file
<span class="code">File</span>. Returns <span class="code">true</span> if the emulator has been
started with the "<span class="code">+Mim true</span>" command-line argument, and
the map was successfully stored; otherwise, <span class="code">false</span>. The
contents of the file can later be read using
<span class="bold_code"><a href="#read_memory_data-1">read_memory_data/1</a></span>.
<strong>NOTE:</strong><span class="code">store_memory_data/0</span> blocks execution of
other processes while the data is collected. The time it takes
to collect the data can be substantial.</p>
</p></div>
<p><a name="store_memory_status-1"><span class="bold_code">store_memory_status(File) -> true|false</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">File = string()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Stores the current memory status on the file
<span class="code">File</span>. Returns <span class="code">true</span> if the emulator has been
started with the "<span class="code">+Mis true</span>", or "<span class="code">+Mim true</span>"
command-line arguments, and the data was successfully stored;
otherwise, <span class="code">false</span>. The contents of the file can later be
read using
<span class="bold_code"><a href="#read_memory_status-1">read_memory_status/1</a></span>.</p>
</p></div>
<p><a name="sum_blocks-1"><span class="bold_code">sum_blocks(MemoryData) -> int()</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Returns the total size of the memory blocks in the list.</p>
</p></div>
<p><a name="type_descr-2"><span class="bold_code">type_descr(MemoryData, TypeNo) -> TypeDescr | invalid_type</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">TypeNo = int()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">TypeDescr = atom() | string()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<p>Returns the type description of a type number used in
<span class="code">MemoryData</span>.
Valid <span class="code">TypeNo</span>s are in the range returned by
<span class="bold_code"><a href="#type_no_range-1">type_no_range/1</a></span> on
this specific memory allocation map. If <span class="code">TypeNo</span> is an
invalid integer, <span class="code">invalid_type</span> is returned.</p>
</p></div>
<p><a name="type_no_range-1"><span class="bold_code">type_no_range(MemoryData) -> {Min, Max}</span></a><br></p>
<div class="REFBODY">
<p>Types:</p>
<div class="REFTYPES">
<span class="bold_code">MemoryData = {term(), AllocList}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">AllocList = [Desc]</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Desc = {int(), int(), int(), PidDesc}</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">PidDesc = {int(), int(), int()} | undefined</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Min = int()</span><br>
</div>
<div class="REFTYPES">
<span class="bold_code">Max = int()</span><br>
</div>
</div>
<div class="REFBODY"><p>
<a name="type_no_range_1"></a>
<p>Returns the memory block type number range used in
<span class="code">MemoryData</span>. When the memory allocation map was generated
by an Erlang 5.3/OTP R9C or newer emulator, all integers <span class="code">T</span>
that satisfy <span class="code">Min</span> <= <span class="code">T</span> <= <span class="code">Max</span> are
valid type numbers. When the memory allocation map was generated
by a pre Erlang 5.3/OTP R9C emulator, all integers in the
range are <strong>not</strong> valid type numbers.</p>
</p></div>
<h3><a name="id85598">See Also</a></h3>
<div class="REFBODY">
<p><span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','erts','erts_alloc.html');">erts_alloc(3)</a></span>,
<span class="bold_code"><a href="javascript:erlhref('../../../../doc/../','erts','erl.html');">erl(1)</a></span></p>
</div>
</div>
<div class="footer">
<hr>
<p>Copyright © 1997-2012 Ericsson AB. All Rights Reserved.</p>
</div>
</div>
</div></body>
</html>
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