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MPU

A shim driver allows in-docker nvidia-smi showing correct process list without modify anything.

The problems

The NVIDIA driver is not aware of the PID namespace and nvidia-smi has no capability to map global pid to virtual pid, thus it shows nothing. What's more, The NVIDIA driver is proprietary and we have no idea what's going on inside even small part of the Linux NVIDIA driver is open sourced.

The alternatives

  • add 'hostPID: true' to the pod specification
  • add '--pid=host' when starting a docker instance

Installation

NOTE: kernel 5.7.7 build routines don't export kallsyms kernel functions any longer, which means this module may not work properly.

  • for debian, to get kernel headers installed with sudo apt install linux-headers-$(uname -r). run sudo apt-get install build-essential to get make toolset installed.
  • clone this repo
  • cd and make
  • after build succeeded, sudo make install to install the module
  • using docker to create --gpu enabled instance and run several cases and check process list via nvidia-smi to see if all associated processes have been correctly shown

The steps

  • figure out the basic mechanism of the NVIDIA driver with the open sourced part
  • do some reverse engineering tests on the driver via GDB tools and several scripts (cuda/NVML)
  • use our module to intercept syscalls and re-write fields of data strucuture with the knowledge of reverse engineering
  • run the nvidia-smi with our module with several test cases

The details

  • nvidia-smi requests 0x20 ioctl command with 0xee4 flag to getting the global PID list (under init_pid_ns) ①
  • after getting non-empty PID list, it'll request 0x20 ioctl command with 0x1f48 flag with previous returned pids as input arguments to getting the process GPU memory consumptions ②
  • we hook the syscalls in system-wide approaching and intercept only NVIDIA device ioctl syscall (device major number is 195 and minor is 255 (control dev) which is defined in NVIDIA header file)
  • check if request task is under any PID namespace, do nothing if it's global one (under init_pid_ns)
  • if so, ① convert the PID list from global to virtual
  • however, ② is a little more complicated which contains two-way interceptors--pre and post.
    • on pre-stage, before invoking NVIDIA ioctl, the virtual PIDs (returned from ①, converted) must convert back to global ones, since NVIDIA driver only recognize global PIDs.
    • and one post-stage, after NVIDIA ioctl invoked, cast global PIDs back

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NOTE

tested on

  • kernel 4.15.0-136 x64 , docker 19.03.15 , NVIDIA driver 440.64
  • kernel 4.19.0-14 x64, NVIDIA driver 460.32

Afterwords, we'd like to maintain the project with fully tested and more kernels and NVIDIA drivers supported. However we sincerely hope NVIDIA will fix this with simplicity and professionalism. Thx.