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 # heaptrack - a heap memory profiler for Linux
 
 ![heaptrack_gui summary page](screenshots/gui_summary.png?raw=true "heaptrack_gui summary page")
 
 Heaptrack traces all memory allocations and annotates these events with stack traces.
 Dedicated analysis tools then allow you to interpret the heap memory profile to:
 
 - find hotspots that need to be optimized to reduce the **memory footprint** of your application
 - find **memory leaks**, i.e. locations that allocate memory which is never deallocated
 - find **allocation hotspots**, i.e. code locations that trigger a lot of memory allocation calls
 - find **temporary allocations**, which are allocations that are directly followed by their deallocation
 
 ## Using heaptrack
 
 The recommended way is to launch your application and start tracing from the beginning:
 
     heaptrack <your application and its parameters>
 
     heaptrack output will be written to "/tmp/heaptrack.APP.PID.gz"
     starting application, this might take some time...
 
     ...
 
     heaptrack stats:
         allocations:            65
         leaked allocations:     60
         temporary allocations:  1
 
     Heaptrack finished! Now run the following to investigate the data:
 
         heaptrack_gui "/tmp/heaptrack.APP.PID.gz"
 
 Alternatively, you can attach to an already running process:
 
     heaptrack --pid $(pidof <your application>)
 
     heaptrack output will be written to "/tmp/heaptrack.APP.PID.gz"
     injecting heaptrack into application via GDB, this might take some time...
     injection finished
 
     ...
 
     Heaptrack finished! Now run the following to investigate the data:
 
         heaptrack_gui "/tmp/heaptrack.APP.PID.gz"
 
 ## Building heaptrack
 
 Heaptrack is split into two parts: The data collector, i.e. `heaptrack` itself, and the
 analyzer GUI called `heaptrack_gui`. The following summarizes the dependencies for these
 two parts as they can be build independently. You will find corresponding development
 packages on all major distributions for these dependencies.
 
 On an embedded device or older Linux distribution, you will only want to build `heaptrack`.
 The data can then be analyzed on a different machine with a more modern Linux distribution
 that has access to the required GUI dependencies.
 
 If you need help with building, deploying or using heaptrack, you can contact KDAB for
 commercial support: https://www.kdab.com/software-services/workshops/profiling-workshops/
 
 ### Shared dependencies
 
 Both parts require the following tools and libraries:
 
 - cmake 2.8.9 or higher
 - a C\+\+11 enabled compiler like g\+\+ or clang\+\+
 - zlib
 - optionally: zstd for faster (de)compression
 - libdl
 - pthread
 - libc
 
 ### `heaptrack` dependencies
 
 The heaptrack data collector and the simplistic `heaptrack_print` analyzer depend on the
 following libraries:
 
 - boost 1.41 or higher: iostreams, program_options
 - libunwind
 
 For runtime-attaching, you will need `gdb` installed.
 
 ### `heaptrack_gui` dependencies
 
 The graphical user interface to interpret and analyze the data collected by heaptrack
 depends on Qt 5 and some KDE libraries:
 
 - extra-cmake-modules
 - Qt 5.2 or higher: Core, Widgets
 - KDE Frameworks 5: CoreAddons, I18n, ItemModels, ThreadWeaver, ConfigWidgets, KIO, IconThemes
 
 When any of these dependencies is missing, `heaptrack_gui` will not be build.
 Optionally, install the following dependencies to get additional features in
 the GUI:
 
 - KDiagram: KChart (for chart visualizations)
 
 ### Compiling
 
 Run the following commands to compile heaptrack. Do pay attention to the output
 of the CMake command, as it will tell you about missing dependencies!
 
     cd heaptrack # i.e. the source folder
     mkdir build
     cd build
     cmake -DCMAKE_BUILD_TYPE=Release .. # look for messages about missing dependencies!
     make -j$(nproc)
 
 #### Compile `heaptrack_gui` on macOS using homebrew
 
 `heaptrack_print` and `heaptrack_gui` can be built on platforms other than Linux, using the dependencies mentioned above.
 On macOS the dependencies can be installed easily using [homebrew](http://brew.sh) and the [KDE homebrew tap](https://github.com/KDE-mac/homebrew-kde).
 
     # prepare tap
     brew tap kde-mac/kde https://invent.kde.org/packaging/homebrew-kde.git
     "$(brew --repo kde-mac/kde)/tools/do-caveats.sh"
     
     # install dependencies
     brew install kde-mac/kde/kf5-kcoreaddons kde-mac/kde/kf5-kitemmodels kde-mac/kde/kf5-kconfigwidgets \
                  kde-mac/kde/kf5-kio kde-mac/kde/kdiagram \
                  kde-extra-cmake-modules kde-ki18n kde-threadweaver \
                  boost zstd gettext
     
     # run manual steps as printed by brew
     ln -sfv "$(brew --prefix)/share/kf5" "$HOME/Library/Application Support"
     ln -sfv "$(brew --prefix)/share/knotifications5" "$HOME/Library/Application Support"
     ln -sfv "$(brew --prefix)/share/kservices5" "$HOME/Library/Application Support"
     ln -sfv "$(brew --prefix)/share/kservicetypes5" "$HOME/Library/Application Support"
 
 To compile make sure to use Qt from homebrew and to have gettext in the path:
 
     cd heaptrack # i.e. the source folder
     mkdir build
     cd build
     CMAKE_PREFIX_PATH=/usr/local/opt/qt PATH=$PATH:/usr/local/opt/gettext/bin cmake ..
     cmake -DCMAKE_BUILD_TYPE=Release .. # look for messages about missing dependencies!
     make heaptrack_gui heaptrack_print
 
 ## Interpreting the heap profile
 
 Heaptrack generates data files that are impossible to analyze for a human. Instead, you need
 to use either `heaptrack_print` or `heaptrack_gui` to interpret the results.
 
 ### heaptrack_gui
 
 ![heaptrack_gui flamegraph page](screenshots/gui_flamegraph.png?raw=true "heaptrack_gui flamegraph page")
 
 ![heaptrack_gui allocations chart page](screenshots/gui_allocations_chart.png?raw=true "heaptrack_gui allocations chart page")
 
 The highly recommended way to analyze a heap profile is by using the `heaptrack_gui` tool.
 It depends on Qt 5 and KF 5 to graphically visualize the recorded data. It features:
 
 - a summary page of the data
 - bottom-up and top-down tree views of the code locations that allocated memory with
   their aggregated cost and stack traces
 - flame graph visualization
 - graphs of allocation costs over time
 
 ### heaptrack_print
 
 The `heaptrack_print` tool is a command line application with minimal dependencies. It takes
 the heap profile, analyzes it, and prints the results in ASCII format to the command line.
 
 In its most simple form, you can use it like this:
 
     heaptrack_print heaptrack.APP.PID.gz | less
 
 By default, the report will contain three sections:
 
     MOST CALLS TO ALLOCATION FUNCTIONS
     PEAK MEMORY CONSUMERS
     MOST TEMPORARY ALLOCATIONS
 
 Each section then lists the top ten hotspots, i.e. code locations that triggered e.g.
 the most memory allocations.
 
 Have a look at `heaptrack_print --help` for changing the output format and other options.
 
 Note that you can use this tool to convert a heaptrack data file to the Massif data format.
 You can generate a collapsed stack report for consumption by `flamegraph.pl`.
 
 ## Comparison to Valgrind's massif
 
 The idea to build heaptrack was born out of the pain in working with Valgrind's massif.
 Valgrind comes with a huge overhead in both memory and time, which sometimes prevent you
 from running it on larger real-world applications. Most of what Valgrind does is not
 needed for a simple heap profiler.
 
 ### Advantages of heaptrack over massif
 
 - *speed and memory overhead*
 
   Multi-threaded applications are not serialized when you trace them with heaptrack and
   even for single-threaded applications the overhead in both time and memory is significantly
   lower. Most notably, you only pay a price when you allocate memory -- time-intensive CPU
   calculations are not slowed down at all, contrary to what happens in Valgrind.
 
 - *more data*
 
   Valgrind's massif aggregates data before writing the report. This step loses a lot of
   useful information. Most notably, you are not longer able to find out how often memory
   was allocated, or where temporary allocations are triggered. Heaptrack does not aggregate the
   data until you interpret it, which allows for more useful insights into your allocation patterns.
 
 ### Advantages of massif over heaptrack
 
 - *ability to profile page allocations as heap*
 
   This allows you to heap-profile applications that use pool allocators that circumvent
   malloc & friends. Heaptrack can in principle also profile such applications, but it
   requires code changes to annotate the memory pool implementation.
 
 - *ability to profile stack allocations*
 
   This is inherently impossible to implement efficiently in heaptrack as far as I know.
 
 ## Contributing to heaptrack
 
 As a FOSS project, we welcome contributions of any form. You can help improve the project by:
 
 - submitting bug reports at https://bugs.kde.org/enter_bug.cgi?product=Heaptrack
 - contributing patches via https://invent.kde.org/sdk/heaptrack
 - translating the GUI with the help of https://l10n.kde.org/
 - writing documentation on https://userbase.kde.org/Heaptrack
 
 When submitting bug reports, you can anonymize your data with the `tools/anonymize` script:
 
     tools/anonymize heaptrack.APP.PID.gz heaptrack.bug_report_data.gz
 
 ## Known bugs and limitations
 
 ### Issues with old gold linker
 
 Libunwind may produce bogus backtraces when unwinding from code linked with old versions of the gold linker.
 In such cases, recording with heaptrack seems to work and produces data files. But parsing these data files
 with heaptrack_gui will often lead to out-of-memory crashes. Looking at the data with heaptrack_print, one
 will see garbage backtraces that are completely broken.
 
 If you encounter such issues, try to relink your application and also libunwind with `ld.bfd` instead of `ld.gold`.
 You can see if you are affected by running the libunwind unit tests via `make check`. But do note that you
 need to relink your application too, not only libunwind.