heaptrack.md

Heaptrack in Nim Waku

Background

Given that RAM is a limited resource, it is crucial to have a good insight on what is going on with the memory used by a particular process.

Heaptrack

Heaptrack is a tool that allows to generate memory usage reports. It operates in two modes:

• preload: the tracking is made from the beginning.
• inject: the tracking starts at a certain time by attaching to a running process.

Building Heaptrack (tried on Ubuntu)

• git clone git@github.com:KDE/heaptrack.git
• mkdir build; cd build
• cmake .. At this point, make sure the cmake doesn't complain about any missing dependency. Among others, the most tricky deps are obtained by the next commands:
  • sudo apt install libkf5i18n-dev
  • sudo apt install libkf5itemmodels-dev
  • sudo apt install libkf5threadweaver-dev
  • sudo apt install libkf5service-dev
  • sudo apt install libkf5completion-dev
  • sudo apt install libkf5itemviews-dev
  • sudo apt install libkf5jobwidgets-dev
  • sudo apt install libkf5solid-dev
  • sudo apt install libkf5coreaddons-dev
  • sudo apt install libkf5auth-dev
  • sudo apt install libkf5codecs-dev
  • sudo apt install libkf5configwidgets-dev
  • sudo apt install libkf5xmlgui-dev
  • sudo apt install libkf5widgetsaddons-dev
  • sudo apt install libqt5gui5
  • sudo apt install libkf5kio-dev
  • sudo apt install libkf5iconthemes-dev
• make
• On completion, the bin/heaptrack_gui and bin/heaptrack binaries will get generated.
  • heaptrack: needed to generate the report.
  • heaptrack_gui: needed to analyse the report.

Heaptrack & Nwaku

nwaku supports heaptrack but it needs a special compilation setting.

Build nwaku with heaptrack support

The make command should have the 'NIM_COMMIT' setting as:

make -j<nproc> NIM_COMMIT=heaptrack_support ...

This is to force the nimbus-build-system to use the Nim compiler that points at the heaptrack_support branch.

Create nwaku memory report with heaptrack

nwaku only works correctly with heaptrack operating in 'preload' mode, i.e. the memory is tracked from the beginning. To achieve this, the heaptrack binary should be prepended to the usual wakunode:

e.g.: <base_heaptrack_folder>/build/bin/heaptrack <base_nwaku_folder>/build/wakunode2 ...

While the above is running, a file with the next format is being populated with allocs/deallocs stats in the current folder:

heaptrack.<process_name>.<pid>.gz
e.g.:
heaptrack.wakunode2.23125.gz

Build a Docker image with Heaptrack + Nim Waku

Having Docker properly installed in your machine, do the next:

• cd to the nwaku root folder.
• sudo make docker-image DOCKER_IMAGE_NAME=docker_repo:docker_tag HEAPTRACKER=1

That will create a Docker image with both nwaku and heaptrack. The container's entry point is ENTRYPOINT ["/heaptrack/build/bin/heaptrack", "/usr/bin/wakunode"], so the memory report starts being generated from the beginning.

Extract report file from a running Docker container

Bear in mind that if you restart the container, the previous report will get lost. Therefore, before restarting, it is important to extract it from the container once you consider it has enough information.

While the Docker container is running, run the next command:

sudo docker cp 768e7de52d3c:/heaptrack.wakunode.1.gz .

(replace the 768.. with your docker container id.).

Analyse a heaptrack report

<heaptrack_base_folder>/bin/heaptrack_gui heaptrack.wakunode.1.gz

You should be able to see memory allocations. It is important to see a legend like shown below: