How can I find a memory leak of a running process?

Question

Is there a way, I can find the memory leak of a running process? I can use Valgrind for finding memory leaks before the start of a process. I can use GDB to attach it to a running process. How could I debug a memory leaks of a running process?

Answer 1

On Linux, you could enable mtrace in your program, but it is a code change.

On OpenBSD, you could try the malloc stats.

Google's leak checker might also be worth a look, and unlike mtrace you may be able to use LD_PRELOAD to avoid recompilation.

Answer 2

I think without providing support for allocation monitoring after program start directly in the source code, you're out of luck. Here are two reasons I can think of:

• Heap checkers initialize when the program begins. Some offer the ability to tweak the exact timing, but the environment variables that start them must be set when the program runs. This is because they watch to make sure each allocation has a corresponding deallocation, and they would miss some otherwise.
• Heap checking usually requires elevated privileges, or hooks, to be provided by the operating system. If those hooks aren't provided at the time of program start, the heap checkers cannot leverage them. I don't believe OSes provide these privileges after the program in question is started.

If, however, you're program is running inside a virtual machine, that environment may provide support for monitoring allocations. I know Java has several allocation and garbage collection monitoring tools (like visualVM) that attach to running programs or VMs.