2007-04-16 20:49:32 +00:00
|
|
|
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
|
|
|
|
|
<HTML>
|
|
|
|
|
|
|
|
|
|
<HEAD>
|
|
|
|
|
<link rel="stylesheet" href="designstyle.css">
|
2012-02-04 00:07:36 +00:00
|
|
|
<title>Gperftools Heap Profiler</title>
|
2007-04-16 20:49:32 +00:00
|
|
|
</HEAD>
|
|
|
|
|
|
|
|
|
|
<BODY>
|
|
|
|
|
|
|
|
|
|
<p align=right>
|
|
|
|
|
<i>Last modified
|
|
|
|
|
<script type=text/javascript>
|
|
|
|
|
var lm = new Date(document.lastModified);
|
|
|
|
|
document.write(lm.toDateString());
|
|
|
|
|
</script></i>
|
|
|
|
|
</p>
|
|
|
|
|
|
|
|
|
|
<p>This is the heap profiler we use at Google, to explore how C++
|
|
|
|
|
programs manage memory. This facility can be useful for</p>
|
|
|
|
|
<ul>
|
|
|
|
|
<li> Figuring out what is in the program heap at any given time
|
|
|
|
|
<li> Locating memory leaks
|
|
|
|
|
<li> Finding places that do a lot of allocation
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
<p>The profiling system instruments all allocations and frees. It
|
|
|
|
|
keeps track of various pieces of information per allocation site. An
|
|
|
|
|
allocation site is defined as the active stack trace at the call to
|
|
|
|
|
<code>malloc</code>, <code>calloc</code>, <code>realloc</code>, or,
|
|
|
|
|
<code>new</code>.</p>
|
|
|
|
|
|
|
|
|
|
<p>There are three parts to using it: linking the library into an
|
|
|
|
|
application, running the code, and analyzing the output.</p>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<h1>Linking in the Library</h1>
|
|
|
|
|
|
|
|
|
|
<p>To install the heap profiler into your executable, add
|
|
|
|
|
<code>-ltcmalloc</code> to the link-time step for your executable.
|
|
|
|
|
Also, while we don't necessarily recommend this form of usage, it's
|
|
|
|
|
possible to add in the profiler at run-time using
|
|
|
|
|
<code>LD_PRELOAD</code>:
|
2008-03-19 23:35:27 +00:00
|
|
|
<pre>% env LD_PRELOAD="/usr/lib/libtcmalloc.so" <binary></pre>
|
2007-04-16 20:49:32 +00:00
|
|
|
|
|
|
|
|
<p>This does <i>not</i> turn on heap profiling; it just inserts the
|
|
|
|
|
code. For that reason, it's practical to just always link
|
|
|
|
|
<code>-ltcmalloc</code> into a binary while developing; that's what we
|
|
|
|
|
do at Google. (However, since any user can turn on the profiler by
|
|
|
|
|
setting an environment variable, it's not necessarily recommended to
|
|
|
|
|
install profiler-linked binaries into a production, running
|
|
|
|
|
system.) Note that if you wish to use the heap profiler, you must
|
|
|
|
|
also use the tcmalloc memory-allocation library. There is no way
|
|
|
|
|
currently to use the heap profiler separate from tcmalloc.</p>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<h1>Running the Code</h1>
|
|
|
|
|
|
|
|
|
|
<p>There are several alternatives to actually turn on heap profiling
|
|
|
|
|
for a given run of an executable:</p>
|
|
|
|
|
|
|
|
|
|
<ol>
|
|
|
|
|
<li> <p>Define the environment variable HEAPPROFILE to the filename
|
|
|
|
|
to dump the profile to. For instance, to profile
|
|
|
|
|
<code>/usr/local/bin/my_binary_compiled_with_tcmalloc</code>:</p>
|
|
|
|
|
<pre>% env HEAPPROFILE=/tmp/mybin.hprof /usr/local/bin/my_binary_compiled_with_tcmalloc</pre>
|
|
|
|
|
<li> <p>In your code, bracket the code you want profiled in calls to
|
|
|
|
|
<code>HeapProfilerStart()</code> and <code>HeapProfilerStop()</code>.
|
2012-02-04 00:07:36 +00:00
|
|
|
(These functions are declared in <code><gperftools/heap-profiler.h></code>.)
|
2010-05-07 21:53:24 +00:00
|
|
|
<code>HeapProfilerStart()</code> will take the
|
|
|
|
|
profile-filename-prefix as an argument. Then, as often as
|
|
|
|
|
you'd like before calling <code>HeapProfilerStop()</code>, you
|
|
|
|
|
can use <code>HeapProfilerDump()</code> or
|
|
|
|
|
<code>GetHeapProfile()</code> to examine the profile. In case
|
|
|
|
|
it's useful, <code>IsHeapProfilerRunning()</code> will tell you
|
2008-09-19 20:06:40 +00:00
|
|
|
whether you've already called HeapProfilerStart() or not.</p>
|
2007-04-16 20:49:32 +00:00
|
|
|
</ol>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<p>For security reasons, heap profiling will not write to a file --
|
|
|
|
|
and is thus not usable -- for setuid programs.</p>
|
|
|
|
|
|
|
|
|
|
<H2>Modifying Runtime Behavior</H2>
|
|
|
|
|
|
|
|
|
|
<p>You can more finely control the behavior of the heap profiler via
|
2008-09-19 20:06:40 +00:00
|
|
|
environment variables.</p>
|
2007-04-16 20:49:32 +00:00
|
|
|
|
|
|
|
|
<table frame=box rules=sides cellpadding=5 width=100%>
|
|
|
|
|
|
|
|
|
|
<tr valign=top>
|
|
|
|
|
<td><code>HEAP_PROFILE_ALLOCATION_INTERVAL</code></td>
|
|
|
|
|
<td>default: 1073741824 (1 Gb)</td>
|
|
|
|
|
<td>
|
2012-11-03 15:40:01 +00:00
|
|
|
Dump heap profiling information each time the specified number of
|
2007-04-16 20:49:32 +00:00
|
|
|
bytes has been allocated by the program.
|
|
|
|
|
</td>
|
|
|
|
|
</tr>
|
|
|
|
|
|
|
|
|
|
<tr valign=top>
|
|
|
|
|
<td><code>HEAP_PROFILE_INUSE_INTERVAL</code></td>
|
|
|
|
|
<td>default: 104857600 (100 Mb)</td>
|
|
|
|
|
<td>
|
|
|
|
|
Dump heap profiling information whenever the high-water memory
|
|
|
|
|
usage mark increases by the specified number of bytes.
|
|
|
|
|
</td>
|
|
|
|
|
</tr>
|
|
|
|
|
|
2012-11-03 15:40:01 +00:00
|
|
|
<tr valign=top>
|
|
|
|
|
<td><code>HEAP_PROFILE_TIME_INTERVAL</code></td>
|
2015-01-10 22:35:54 +00:00
|
|
|
<td>default: 0</td>
|
2012-11-03 15:40:01 +00:00
|
|
|
<td>
|
|
|
|
|
Dump heap profiling information each time the specified
|
|
|
|
|
number of seconds has elapsed.
|
|
|
|
|
</td>
|
|
|
|
|
</tr>
|
|
|
|
|
|
2017-05-26 11:09:03 +00:00
|
|
|
<tr valign=top>
|
|
|
|
|
<td><code>HEAPPROFILESIGNAL</code></td>
|
|
|
|
|
<td>default: disabled</td>
|
|
|
|
|
<td>
|
|
|
|
|
Dump heap profiling information whenever the specified signal is sent to the
|
|
|
|
|
process.
|
|
|
|
|
</td>
|
|
|
|
|
</tr>
|
|
|
|
|
|
2007-04-16 20:49:32 +00:00
|
|
|
<tr valign=top>
|
|
|
|
|
<td><code>HEAP_PROFILE_MMAP</code></td>
|
|
|
|
|
<td>default: false</td>
|
|
|
|
|
<td>
|
2009-11-10 16:24:57 +00:00
|
|
|
Profile <code>mmap</code>, <code>mremap</code> and <code>sbrk</code>
|
|
|
|
|
calls in addition
|
|
|
|
|
to <code>malloc</code>, <code>calloc</code>, <code>realloc</code>,
|
|
|
|
|
and <code>new</code>. <b>NOTE:</b> this causes the profiler to
|
|
|
|
|
profile calls internal to tcmalloc, since tcmalloc and friends use
|
|
|
|
|
mmap and sbrk internally for allocations. One partial solution is
|
|
|
|
|
to filter these allocations out when running <code>pprof</code>,
|
|
|
|
|
with something like
|
|
|
|
|
<code>pprof --ignore='DoAllocWithArena|SbrkSysAllocator::Alloc|MmapSysAllocator::Alloc</code>.
|
2007-04-16 20:49:32 +00:00
|
|
|
</td>
|
|
|
|
|
</tr>
|
|
|
|
|
|
2008-04-22 01:47:16 +00:00
|
|
|
<tr valign=top>
|
2012-10-28 19:45:03 +00:00
|
|
|
<td><code>HEAP_PROFILE_ONLY_MMAP</code></td>
|
2008-04-22 01:47:16 +00:00
|
|
|
<td>default: false</td>
|
|
|
|
|
<td>
|
|
|
|
|
Only profile <code>mmap</code>, <code>mremap</code>, and <code>sbrk</code>
|
|
|
|
|
calls; do not profile
|
|
|
|
|
<code>malloc</code>, <code>calloc</code>, <code>realloc</code>,
|
|
|
|
|
or <code>new</code>.
|
|
|
|
|
</td>
|
|
|
|
|
</tr>
|
|
|
|
|
|
2007-04-16 20:49:32 +00:00
|
|
|
<tr valign=top>
|
|
|
|
|
<td><code>HEAP_PROFILE_MMAP_LOG</code></td>
|
|
|
|
|
<td>default: false</td>
|
|
|
|
|
<td>
|
2008-04-22 01:47:16 +00:00
|
|
|
Log <code>mmap</code>/<code>munmap</code> calls.
|
2007-04-16 20:49:32 +00:00
|
|
|
</td>
|
|
|
|
|
</tr>
|
|
|
|
|
|
|
|
|
|
</table>
|
|
|
|
|
|
|
|
|
|
<H2>Checking for Leaks</H2>
|
|
|
|
|
|
|
|
|
|
<p>You can use the heap profiler to manually check for leaks, for
|
|
|
|
|
instance by reading the profiler output and looking for large
|
|
|
|
|
allocations. However, for that task, it's easier to use the <A
|
|
|
|
|
HREF="heap_checker.html">automatic heap-checking facility</A> built
|
|
|
|
|
into tcmalloc.</p>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<h1><a name="pprof">Analyzing the Output</a></h1>
|
|
|
|
|
|
|
|
|
|
<p>If heap-profiling is turned on in a program, the program will
|
|
|
|
|
periodically write profiles to the filesystem. The sequence of
|
|
|
|
|
profiles will be named:</p>
|
|
|
|
|
<pre>
|
|
|
|
|
<prefix>.0000.heap
|
|
|
|
|
<prefix>.0001.heap
|
|
|
|
|
<prefix>.0002.heap
|
|
|
|
|
...
|
|
|
|
|
</pre>
|
|
|
|
|
<p>where <code><prefix></code> is the filename-prefix supplied
|
|
|
|
|
when running the code (e.g. via the <code>HEAPPROFILE</code>
|
|
|
|
|
environment variable). Note that if the supplied prefix
|
|
|
|
|
does not start with a <code>/</code>, the profile files will be
|
|
|
|
|
written to the program's working directory.</p>
|
|
|
|
|
|
|
|
|
|
<p>The profile output can be viewed by passing it to the
|
|
|
|
|
<code>pprof</code> tool -- the same tool that's used to analyze <A
|
|
|
|
|
HREF="cpuprofile.html">CPU profiles</A>.
|
|
|
|
|
|
|
|
|
|
<p>Here are some examples. These examples assume the binary is named
|
|
|
|
|
<code>gfs_master</code>, and a sequence of heap profile files can be
|
|
|
|
|
found in files named:</p>
|
|
|
|
|
<pre>
|
|
|
|
|
/tmp/profile.0001.heap
|
|
|
|
|
/tmp/profile.0002.heap
|
|
|
|
|
...
|
|
|
|
|
/tmp/profile.0100.heap
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<h3>Why is a process so big</h3>
|
|
|
|
|
|
|
|
|
|
<pre>
|
|
|
|
|
% pprof --gv gfs_master /tmp/profile.0100.heap
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>This command will pop-up a <code>gv</code> window that displays
|
|
|
|
|
the profile information as a directed graph. Here is a portion
|
|
|
|
|
of the resulting output:</p>
|
|
|
|
|
|
|
|
|
|
<p><center>
|
|
|
|
|
<img src="heap-example1.png">
|
|
|
|
|
</center></p>
|
|
|
|
|
|
|
|
|
|
A few explanations:
|
|
|
|
|
<ul>
|
|
|
|
|
<li> <code>GFS_MasterChunk::AddServer</code> accounts for 255.6 MB
|
|
|
|
|
of the live memory, which is 25% of the total live memory.
|
|
|
|
|
<li> <code>GFS_MasterChunkTable::UpdateState</code> is directly
|
|
|
|
|
accountable for 176.2 MB of the live memory (i.e., it directly
|
|
|
|
|
allocated 176.2 MB that has not been freed yet). Furthermore,
|
|
|
|
|
it and its callees are responsible for 729.9 MB. The
|
|
|
|
|
labels on the outgoing edges give a good indication of the
|
|
|
|
|
amount allocated by each callee.
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
<h3>Comparing Profiles</h3>
|
|
|
|
|
|
|
|
|
|
<p>You often want to skip allocations during the initialization phase
|
|
|
|
|
of a program so you can find gradual memory leaks. One simple way to
|
|
|
|
|
do this is to compare two profiles -- both collected after the program
|
|
|
|
|
has been running for a while. Specify the name of the first profile
|
|
|
|
|
using the <code>--base</code> option. For example:</p>
|
|
|
|
|
<pre>
|
|
|
|
|
% pprof --base=/tmp/profile.0004.heap gfs_master /tmp/profile.0100.heap
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>The memory-usage in <code>/tmp/profile.0004.heap</code> will be
|
|
|
|
|
subtracted from the memory-usage in
|
|
|
|
|
<code>/tmp/profile.0100.heap</code> and the result will be
|
|
|
|
|
displayed.</p>
|
|
|
|
|
|
|
|
|
|
<h3>Text display</h3>
|
|
|
|
|
|
|
|
|
|
<pre>
|
|
|
|
|
% pprof --text gfs_master /tmp/profile.0100.heap
|
|
|
|
|
255.6 24.7% 24.7% 255.6 24.7% GFS_MasterChunk::AddServer
|
|
|
|
|
184.6 17.8% 42.5% 298.8 28.8% GFS_MasterChunkTable::Create
|
|
|
|
|
176.2 17.0% 59.5% 729.9 70.5% GFS_MasterChunkTable::UpdateState
|
|
|
|
|
169.8 16.4% 75.9% 169.8 16.4% PendingClone::PendingClone
|
|
|
|
|
76.3 7.4% 83.3% 76.3 7.4% __default_alloc_template::_S_chunk_alloc
|
|
|
|
|
49.5 4.8% 88.0% 49.5 4.8% hashtable::resize
|
|
|
|
|
...
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
<ul>
|
|
|
|
|
<li> The first column contains the direct memory use in MB.
|
|
|
|
|
<li> The fourth column contains memory use by the procedure
|
|
|
|
|
and all of its callees.
|
|
|
|
|
<li> The second and fifth columns are just percentage
|
2007-07-18 18:30:50 +00:00
|
|
|
representations of the numbers in the first and fourth columns.
|
2007-04-16 20:49:32 +00:00
|
|
|
<li> The third column is a cumulative sum of the second column
|
|
|
|
|
(i.e., the <code>k</code>th entry in the third column is the
|
|
|
|
|
sum of the first <code>k</code> entries in the second column.)
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
<h3>Ignoring or focusing on specific regions</h3>
|
|
|
|
|
|
|
|
|
|
<p>The following command will give a graphical display of a subset of
|
|
|
|
|
the call-graph. Only paths in the call-graph that match the regular
|
|
|
|
|
expression <code>DataBuffer</code> are included:</p>
|
|
|
|
|
<pre>
|
|
|
|
|
% pprof --gv --focus=DataBuffer gfs_master /tmp/profile.0100.heap
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>Similarly, the following command will omit all paths subset of the
|
|
|
|
|
call-graph. All paths in the call-graph that match the regular
|
|
|
|
|
expression <code>DataBuffer</code> are discarded:</p>
|
|
|
|
|
<pre>
|
|
|
|
|
% pprof --gv --ignore=DataBuffer gfs_master /tmp/profile.0100.heap
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<h3>Total allocations + object-level information</h3>
|
|
|
|
|
|
|
|
|
|
<p>All of the previous examples have displayed the amount of in-use
|
|
|
|
|
space. I.e., the number of bytes that have been allocated but not
|
|
|
|
|
freed. You can also get other types of information by supplying a
|
|
|
|
|
flag to <code>pprof</code>:</p>
|
|
|
|
|
|
|
|
|
|
<center>
|
|
|
|
|
<table frame=box rules=sides cellpadding=5 width=100%>
|
|
|
|
|
|
|
|
|
|
<tr valign=top>
|
|
|
|
|
<td><code>--inuse_space</code></td>
|
|
|
|
|
<td>
|
|
|
|
|
Display the number of in-use megabytes (i.e. space that has
|
|
|
|
|
been allocated but not freed). This is the default.
|
|
|
|
|
</td>
|
|
|
|
|
</tr>
|
|
|
|
|
|
|
|
|
|
<tr valign=top>
|
|
|
|
|
<td><code>--inuse_objects</code></td>
|
|
|
|
|
<td>
|
|
|
|
|
Display the number of in-use objects (i.e. number of
|
|
|
|
|
objects that have been allocated but not freed).
|
|
|
|
|
</td>
|
|
|
|
|
</tr>
|
|
|
|
|
|
|
|
|
|
<tr valign=top>
|
|
|
|
|
<td><code>--alloc_space</code></td>
|
|
|
|
|
<td>
|
|
|
|
|
Display the number of allocated megabytes. This includes
|
|
|
|
|
the space that has since been de-allocated. Use this
|
|
|
|
|
if you want to find the main allocation sites in the
|
|
|
|
|
program.
|
|
|
|
|
</td>
|
|
|
|
|
</tr>
|
|
|
|
|
|
|
|
|
|
<tr valign=top>
|
|
|
|
|
<td><code>--alloc_objects</code></td>
|
|
|
|
|
<td>
|
|
|
|
|
Display the number of allocated objects. This includes
|
|
|
|
|
the objects that have since been de-allocated. Use this
|
|
|
|
|
if you want to find the main allocation sites in the
|
|
|
|
|
program.
|
|
|
|
|
</td>
|
|
|
|
|
|
|
|
|
|
</table>
|
|
|
|
|
</center>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<h3>Interactive mode</a></h3>
|
|
|
|
|
|
|
|
|
|
<p>By default -- if you don't specify any flags to the contrary --
|
|
|
|
|
pprof runs in interactive mode. At the <code>(pprof)</code> prompt,
|
|
|
|
|
you can run many of the commands described above. You can type
|
|
|
|
|
<code>help</code> for a list of what commands are available in
|
|
|
|
|
interactive mode.</p>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<h1>Caveats</h1>
|
|
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
<li> Heap profiling requires the use of libtcmalloc. This
|
|
|
|
|
requirement may be removed in a future version of the heap
|
|
|
|
|
profiler, and the heap profiler separated out into its own
|
|
|
|
|
library.
|
|
|
|
|
|
|
|
|
|
<li> If the program linked in a library that was not compiled
|
|
|
|
|
with enough symbolic information, all samples associated
|
|
|
|
|
with the library may be charged to the last symbol found
|
2013-07-06 20:46:50 +00:00
|
|
|
in the program before the library. This will artificially
|
2007-04-16 20:49:32 +00:00
|
|
|
inflate the count for that symbol.
|
|
|
|
|
|
|
|
|
|
<li> If you run the program on one machine, and profile it on
|
|
|
|
|
another, and the shared libraries are different on the two
|
|
|
|
|
machines, the profiling output may be confusing: samples that
|
|
|
|
|
fall within the shared libaries may be assigned to arbitrary
|
|
|
|
|
procedures.
|
|
|
|
|
|
|
|
|
|
<li> Several libraries, such as some STL implementations, do their
|
|
|
|
|
own memory management. This may cause strange profiling
|
|
|
|
|
results. We have code in libtcmalloc to cause STL to use
|
|
|
|
|
tcmalloc for memory management (which in our tests is better
|
|
|
|
|
than STL's internal management), though it only works for some
|
|
|
|
|
STL implementations.
|
|
|
|
|
|
|
|
|
|
<li> If your program forks, the children will also be profiled
|
|
|
|
|
(since they inherit the same HEAPPROFILE setting). Each
|
|
|
|
|
process is profiled separately; to distinguish the child
|
|
|
|
|
profiles from the parent profile and from each other, all
|
|
|
|
|
children will have their process-id attached to the HEAPPROFILE
|
|
|
|
|
name.
|
|
|
|
|
|
|
|
|
|
<li> Due to a hack we make to work around a possible gcc bug, your
|
|
|
|
|
profiles may end up named strangely if the first character of
|
|
|
|
|
your HEAPPROFILE variable has ascii value greater than 127.
|
|
|
|
|
This should be exceedingly rare, but if you need to use such a
|
|
|
|
|
name, just set prepend <code>./</code> to your filename:
|
|
|
|
|
<code>HEAPPROFILE=./Ägypten</code>.
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
<hr>
|
2011-07-16 01:07:10 +00:00
|
|
|
<address>Sanjay Ghemawat
|
2007-04-16 20:49:32 +00:00
|
|
|
<!-- Created: Tue Dec 19 10:43:14 PST 2000 -->
|
|
|
|
|
</address>
|
|
|
|
|
</body>
|
|
|
|
|
</html>
|
