Using MariaDB with TCMalloc or jemalloc

Using tcmalloc

TCMalloc is a malloc replacement library optimized for multi-threaded usage. It also features a built-in heap debugger and profiler. You can build MariaDB with it or LD_PRELOAD it.

To build MariaDB 5.5 with TCMalloc, you need to use the following command

cmake -DCMAKE_EXE_LINKER_FLAGS='-ltcmalloc'  -DWITH_SAFEMALLOC=OFF

Many other malloc replacement libraries (as well as heap debuggers and profilers) can be used with MariaDB in a similar fashion.

You can also start a standard MariaDB server with TCmalloc with:

/usr/sbin/mysqld_safe --malloc-lib=tcmalloc

or add it to my.cnf. Alternatively just set LD_PRELOAD to point to the to be used malloc library:

export LD_PRELOAD=/path/to/library

Using jemalloc

The above procedure also works with jemalloc. Just replace tcmalloc with jemalloc in the above commands.

Finding memory leaks with jemalloc

jemalloc can provide a report of memory leaks at program exit:

MALLOC_CONF=prof_leak:true,lg_prof_sample:0,prof_final:true \
LD_PRELOAD=${JEMALLOC_PATH}/lib/libjemalloc.so.2  path-to-mariadbd

This will produce something like:

<jemalloc>: Leak summary: 267184 bytes, 473 objects, 20 contexts
<jemalloc>: Run jeprof on "jeprof.19678.0.f.heap" for leak detail

You can learn more about the memory leaks with jeprof, that is included with jemalloc:

jeprof --show_bytes path-to-mariadbd jeprof.19678.0.f.heap

You can also generate a PDF call graph of the leak:

jeprof --show_bytes --pdf path-to-mariadbd  jeprof.19678.0.f.heap > /tmp/mariadbd.pdf

See Also

• Debugging a running server on Linux
• Jemalloc leak checking