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doc: capitalize valgrind
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PR-URL: nodejs#41986
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Mestery <mestery@protonmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
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mahmoud-moursy authored and bengl committed Feb 21, 2022
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# Investigating memory leaks with valgrind
# Investigating memory leaks with Valgrind

A Node.js process may run out of memory due to excessive consumption of
native memory. Native Memory is memory which is not managed by the
V8 Garbage collector and is allocated either by the Node.js runtime, its
dependencies or native [addons](https://nodejs.org/docs/latest/api/n-api.html).

This guide provides information on how to use valgrind to investigate these
This guide provides information on how to use Valgrind to investigate these
issues on Linux platforms.

## valgrind
## Valgrind

[Valgrind](https://valgrind.org/docs/manual/quick-start.html) is a
tool available on Linux distributions which can be used to investigate
memory usage including identifying memory leaks (memory which is
allocated and not freed) and other memory related problems
like double freeing memory.

To use valgrind:
To use Valgrind:

* Be patient, running under valgrind slows execution significantly
* Be patient, running under Valgrind slows execution significantly
due to the checks being performed.
* Reduce your test case to the smallest reproduce. Due to the slowdown it is
important to run the minimum test case in order to be able to do it in
Expand All @@ -35,7 +35,7 @@ apt-get install valgrind

## Invocation

The simplest invocation of valgrind is:
The simplest invocation of Valgrind is:

```console
valgrind node test.js
Expand Down Expand Up @@ -133,7 +133,7 @@ it along with the allocations (since it is not used)
and Valgrind will not find any leaks since they
will no longer exist in the code being run.
Running valgrind on this code shows the following:
Running Valgrind on this code shows the following:
```console
user1@minikube1:~/valgrind/node-addon-examples/1_hello_world/napi$ valgrind node hello.js
Expand Down Expand Up @@ -317,7 +317,7 @@ From the stack trace we can tell that the leak came from a native addon:
What we can't tell is where in the native addon the memory is being
allocated. This is because by default the addon is compiled without
the debug symbols which valgrind needs to be able to provide more
the debug symbols which Valgrind needs to be able to provide more
information.

## Enabling debug symbols to get more information
Expand Down Expand Up @@ -345,7 +345,7 @@ npm install --debug
npm rebuild
```

The next step is to run valgrind after the rebuild. This time the information
The next step is to run Valgrind after the rebuild. This time the information
for the leaking location includes the name of the source file and the
line number:

Expand Down Expand Up @@ -385,7 +385,7 @@ This new output shows us exactly where the leak is occurring in the file `hello.
If the leak is not in an addon and is instead in the Node.js binary itself,
you may need to compile node yourself and turn on debug symbols. Looking at
this entry reported by valgrind, with a release binary we see:
this entry reported by Valgrind, with a release binary we see:
```console
==4174== 304 bytes in 1 blocks are possibly lost in loss record 27 of 35
Expand All @@ -409,7 +409,7 @@ its symbols using `-rdynamic` so that they can be used by addons. If the stack
gives you enough information to track down where the leak is, that's great,
otherwise the next step is to compile a debug build of Node.js.
To get additional information with valgrind:
To get additional information with Valgrind:
* Check out the Node.js source corresponding to the release that you
want to debug. For example:
Expand All @@ -432,7 +432,7 @@ make -j4
`./configure --debug`, two binaries will have been built when `make` was run.
You must use the one which is in `out/Debug`.
Running valgrind using the debug build of Node.js shows:
Running Valgrind using the debug build of Node.js shows:
```console
==44112== 592 bytes in 1 blocks are possibly lost in loss record 26 of 27
Expand All @@ -450,3 +450,6 @@ Running valgrind using the debug build of Node.js shows:
Now we can see the specific file name and line in the Node.js code which
caused the allocation (inspector\_agent.cc:140).
We can examine that line (and its surrounding code) to
find a solution for the memory leak.

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