1. Memory Debugging
In Python, Cython, and C/C++ On Linux
Alain Leon
github.com/xerebz
xerebz@gmail.com
Pindrop

2. Background
Memory was found to be leaking somewhere in our Python scripts
There are a bunch of tools I had never used before to find and diagnose the problem

3. Good Ol’ Top (or htop)
Run your code and watch resident memory increase
● top -> shift+F -> n -> enter
● top -> shift+M
● watch -n 1 ps -o rss -C PROCESSNAME
● watch -n 1 ps -o rss -p PID

4. Python Memory Tools
● Objgraph - objgraph.show_growth()
● Guppy/Heapy - hpy.heap()
● Memory_profiler - @profile
● Dowser
● Many others

5. C/C++ Memory Tools
Valgrind (Memcheck, Massif, DHAT) - suite of tools, replace calls to malloc
GDB-Heap - unplanned memory usage debugging, adds heap helpers to GDB
Heaptrack - LD_PRELOAD (DLL Injection)
Google Heap Profiler - uses thread-caching malloc
sudo ltrace -e malloc,calloc,realloc,free -p $(pidof extract_all)

6. Valgrind
Pronounced Val-Grinned
Memcheck - default tool, lists out possible memory problems
Massif - heap profiler, describes heap size over time
DHAT - Dynamic Heap Allocation Tool, heap allocation tool, process lifetime leaks
Python allocates itself its own memory block (PyMalloc)
Compile Python with --without-pymalloc
docker pull xerebz/pygrind

7. GDB
gdb python -> r test.py
python2.7-dbg test.py & -> gdb -p $(pidof python2.7-dbg)
Add libpython debugging symbols and GDB helper functions like py-bt
http://grapsus.net/blog/post/Low-level-Python-debugging-with-GDB
http://goo.gl/MRr3Od

8. Linux Virtual Memory Manager

9. Linux Memory System Calls
brk - set the program break, adds memory pages to the top of the heap
sbrk - increments the program break
mmap - map independent page of memory
munmap - unmaps memory pages
strace -e brk,mmap,munmap -p $(pidof PROCNAME)
Compiler flag -O0 removes optimizations

10. Haiku Intermission

11. Example
ltrace strace

12. At Pindrop

13. Before (Massif output)

14. After (Massif output)

15. The End!
Alain Leon
github.com/xerebz
xerebz@gmail.com
Pindrop