The author never made clear if they are measuring virtual memory usage, or physical memory usage. Having a lot of virtual memory does not "cost" much: it's just

The author never made clear if they are measuring virtual memory usage, or physical memory usage. Having a lot of virtual memory does not "cost" much: it's just having permission to use a lot of memory if you so wish. It's possible to have huge chunks of your virtual address space with no physical memory backing them. Physical memory is the amount of physical RAM your process is using. Yes, that remains very unclear. Only physical memory is interesting in the end, address space exhaustion is not on issue on most systems today and large pages are typically not used. The graphs have "virtual", "dirty" and "clean" in them. "clean" normally means that the page in RAM is just a copy of a mass storage. If the kernel runs short of memory, it can use this page for other purposes. No harm done, except that the system gets slower when it needs to page in the same page later. "dirty" normally means that the page in RAM is not backed by mass storage. The kernel must keep it reserved for the current purpose in order not to lose data. If we assume that author's application does not do swapping (it really shouldn't for 230 MB, otherwise the machine is seriously overloaded and really slow) all heap in use is always dirty. The amount of dirty equals usage of physical RAM. I am not sure which Linux tool that can easily report the use of physical RAM for the heap. Would RssAnon from /proc/self/status be a good approximation? It certainly contains the stack, too. But that should not grow a lot unless you have infinite recursion.