rs_malloc_tracker 1.0.0

# rs-malloc-tracker

This tool is meant to solve a specific use-case: Troubleshooting unexplained memory usage in a C application (namely asterisk).

Ideally, you'd make every memory allocation go through a custom allocator that does proper tracking for your use-case. In my case though, I had a couple problems:

1. Shared libraries obviously don't follow this pattern
2. The memory that I was tracking through my custom allocator did not add up to the observed RSS of my application. Not even *close*:
   ![Screnshot of Asterisk RSS going up to around 1.25 GiB](./media/asterisk-rss.png)
   ![Screnshot of `ast_malloc()` instrumentation going up to around 100 MiB](./media/ast_malloc.png)

From these observations, it was clear that a lower-level instrumentation was required to properly shine light on what was going on. Hence, this tool.

## What this does

* Use the `LD_PRELOAD` trick to:
  * Wrap `malloc(3)`, `free(3)` and related functions to tabulate memory usage
  * Wrap `mmap(3)` and `munmap(3)` to tabulate VSS and RSS separately
* Expose the results in prometheus format in a per-process UNIX socket

The end result looks like this:

![Screenshot of `rs-malloc-tracker` showing `malloc()` and `smaps` instrumentation](./media/rs-malloc-tracker.png)

This allowed me to understand what my problem was: https://github.com/facebook/jemalloc/issues/46