kdablabs / qmemstat

Inspect Pagemaps of Programs

QMemstat

QMemstat is a tool to inspect the address space of a process.

The Linux kernel exposes quite detailed information about the memory pages that processes use, and information about the pages themselves, which can be put together to get detailed information about a given process. qmemstat uses this information from the kernel and shows it in a more convenient format. Since the kernel interfaces used are root-only for security reasons, qmemstat needs to run as root, or at least a "server" needs to run as root for qmemstat.

Tools

QMemstat contains two related tools:

memstat

Command-line tool. It must be run as root.

memstat has two modes:

• display memory use information: memstat <pid>|<process-name> outputs the following three numbers:
  • VSZ (virtual set size): the size of the address space of the process
  • RSS (resident set size): the size of physical memory in the address space of the process
  • PSS (proportional set size): like RSS, but for shared memory pages the size is divided by the number of users. This is the most accurate "actual memory used" value.
• server mode: memstat <pid>|<process> --server <port-number> continuously grabs address space information and provides it to qmemstat (see below).

qmemstat

GUI tool which shows information about a process's address space, and which updates the information continuously.

It has two modes:

• standalone: qmemstat <pid>|<process-name> (must be run as root) shows a graphical view of the address space of the process.
  • Hold down the left mouse button to see the flags of the page under the cursor in the panel on the left.
• as a client to memstat running in server mode (does not need root): qmemstat --client <server-address> <port-number> Otherwise it works like standalone mode.

qmemstat's Issues

Adopt to differing ProcFS formats

Sometimes the (mmap) backing filename is in col 5, sometimes in 6 .
Either find the procfs format and adapt to it or just use the "last" column.

Filenames in License Headers

Currently all called main.cpp.
Change to fitting Filename.

Throttle the Updates

16ms / Frame should be enough

Move sources to dedicated directory

I think it would be helpful to have the source files in a dedicated subdirectory and not directly in the root, as this is more common and helps to distinguish sources, documentation, etc.