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memory-profile-valgrind-massif.md

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Massif Basics

Valgrind is an instrumentation framework that runs a program by simulating every instruction. It has several tools. Memcheck is the original one, used for detecting memory errors. Massif is a memory profiler.

(The output it produces, example: https://github.com/yast/yast-installation/wiki/Massif-Sample-Output )

The basic invocation of Massif is simple, valgrind --tool=massif my_program its_arguments, so for YaST it is

# valgrind --tool=massif /usr/lib/YaST2/bin/y2start sw_single qt

Or, if we don't want to dig in the startup scripts, we use a bigger gun:

# valgrind --tool=massif --trace-children=yes yast2 sw_single

That writes out massif.out.99999 where 99999 is process ID. To make them somewhat more readable, use the included tool ms_print which adds an ASCII graph and computes percentages:

ms_print massif.out.19015 >  massif.out.19015.txt

Debuginfo

The backtraces will contain some names, at the boundaries of shared libraries But to see names inside libraries Massif needs debuginfo files.

Massif at Installation Time

tl;dr: Boot with extend=gdb MASSIF=1.

  1. Install Massif. It is part of the gdb extension, so use extend=gdb at the boot prompt, or run extend gdb in an inst-sys shell.

  2. Install Debuginfo. For Tumbleweed an automatic downloader is in place from https://debuginfod.opensuse.org/.

  3. Wrap Massif around the main installer process. The startup/YaST2.call script will do it if the environment variable MASSIF=1, putting the logs where save_y2logs expects them.