Re: [RFC PATCH 0/5] cgroup support for GPU devices

["Welty, Brian" <brian.welty@intel.com>]

On 5/2/2019 3:48 PM, Kenny Ho wrote:
> On 5/2/2019 1:34 AM, Leon Romanovsky wrote:
>> Count us (Mellanox) too, our RDMA devices are exposing special and
>> limited in size device memory to the users and we would like to provide
>> an option to use cgroup to control its exposure.

Hi Leon, great to hear and happy to work with you and RDMA community
to shape this framework for use by RDMA devices as well.  The intent
was to support more than GPU devices.

Incidentally, I also wanted to ask about the rdma cgroup controller
and if there is interest in updating the device registration implemented
in that controller.  It could use the cgroup_device_register() that is
proposed here.   But this is perhaps future work, so can discuss separately.


> Doesn't RDMA already has a separate cgroup?  Why not implement it there?
> 

Hi Kenny, I can't answer for Leon, but I'm hopeful he agrees with rationale
I gave in the cover letter.  Namely, to implement in rdma controller, would
mean duplicating existing memcg controls there.

Is AMD interested in collaborating to help shape this framework?
It is intended to be device-neutral, so could be leveraged by various
types of devices.
If you have an alternative solution well underway, then maybe
we can work together to merge our efforts into one.
In the end, the DRM community is best served with common solution.


> 
>>> and with future work, we could extend to:
>>> *  track and control share of GPU time (reuse of cpu/cpuacct)
>>> *  apply mask of allowed execution engines (reuse of cpusets)
>>>
>>> Instead of introducing a new cgroup subsystem for GPU devices, a new
>>> framework is proposed to allow devices to register with existing cgroup
>>> controllers, which creates per-device cgroup_subsys_state within the
>>> cgroup.  This gives device drivers their own private cgroup controls
>>> (such as memory limits or other parameters) to be applied to device
>>> resources instead of host system resources.
>>> Device drivers (GPU or other) are then able to reuse the existing cgroup
>>> controls, instead of inventing similar ones.
>>>
>>> Per-device controls would be exposed in cgroup filesystem as:
>>>     mount/<cgroup_name>/<subsys_name>.devices/<dev_name>/<subsys_files>
>>> such as (for example):
>>>     mount/<cgroup_name>/memory.devices/<dev_name>/memory.max
>>>     mount/<cgroup_name>/memory.devices/<dev_name>/memory.current
>>>     mount/<cgroup_name>/cpu.devices/<dev_name>/cpu.stat
>>>     mount/<cgroup_name>/cpu.devices/<dev_name>/cpu.weight
>>>
>>> The drm/i915 patch in this series is based on top of other RFC work [1]
>>> for i915 device memory support.
>>>
>>> AMD [2] and Intel [3] have proposed related work in this area within the
>>> last few years, listed below as reference.  This new RFC reuses existing
>>> cgroup controllers and takes a different approach than prior work.
>>>
>>> Finally, some potential discussion points for this series:
>>> * merge proposed <subsys_name>.devices into a single devices directory?
>>> * allow devices to have multiple registrations for subsets of resources?
>>> * document a 'common charging policy' for device drivers to follow?
>>>
>>> [1] https://patchwork.freedesktop.org/series/56683/
>>> [2] https://lists.freedesktop.org/archives/dri-devel/2018-November/197106.html
>>> [3] https://lists.freedesktop.org/archives/intel-gfx/2018-January/153156.html
>>>
>>>
>>> Brian Welty (5):
>>>   cgroup: Add cgroup_subsys per-device registration framework
>>>   cgroup: Change kernfs_node for directories to store
>>>     cgroup_subsys_state
>>>   memcg: Add per-device support to memory cgroup subsystem
>>>   drm: Add memory cgroup registration and DRIVER_CGROUPS feature bit
>>>   drm/i915: Use memory cgroup for enforcing device memory limit
>>>
>>>  drivers/gpu/drm/drm_drv.c                  |  12 +
>>>  drivers/gpu/drm/drm_gem.c                  |   7 +
>>>  drivers/gpu/drm/i915/i915_drv.c            |   2 +-
>>>  drivers/gpu/drm/i915/intel_memory_region.c |  24 +-
>>>  include/drm/drm_device.h                   |   3 +
>>>  include/drm/drm_drv.h                      |   8 +
>>>  include/drm/drm_gem.h                      |  11 +
>>>  include/linux/cgroup-defs.h                |  28 ++
>>>  include/linux/cgroup.h                     |   3 +
>>>  include/linux/memcontrol.h                 |  10 +
>>>  kernel/cgroup/cgroup-v1.c                  |  10 +-
>>>  kernel/cgroup/cgroup.c                     | 310 ++++++++++++++++++---
>>>  mm/memcontrol.c                            | 183 +++++++++++-
>>>  13 files changed, 552 insertions(+), 59 deletions(-)
>>>
>>> --
>>> 2.21.0
>>>
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