[PATCH RFC v2 0/7] DRM management via cgroups

[Matt Roper <matthew.d.roper@intel.com>]

This is a second iteration of the patches originally posted here:
        https://lists.freedesktop.org/archives/intel-gfx/2018-January/153156.html

Please see the original cover letter to understand the general goal and
justification for this work.

This series makes the following important changes to the design from
the first version:

 * The "cgroup helper library" has been removed from the DRM core; the
   early patches of this series introduce an enhancement to the cgroup
   subsystem itself which will grant drivers the ability to save/restore
   their own driver-specific data structures associated with individual
   cgroups.  Drivers may subclass the cgroup_driver_data structure to
   store any kind of per-cgroup data they want, not just integer
   key/value pairs as the helper library from version 1 of this series
   did.  Moving this functionality directly into cgroups will also allow
   other parts of the kernel to potentially benefit from this
   functionality, not just DRM drivers.

 * The general graphics-specific ioctl to set cgroup parameters has
   moved from the DRM core to i915.  This was pretty much an arbitrary
   choice I made while re-writing the new version of the series; I don't
   have a strong opinion over whether the ioctl goes in the DRM core or
   stays i915-specific.  I'd appreciate feedback from other driver teams
   as to whether they anticipate cgroup integration being useful for
   their drivers and use cases (e.g., for controlling things like GPU
   memory usage, priority settings, etc.).  I'll move the ioctl back to
   the DRM core in the next iteration if there's interest from other
   driver teams.

 * The i915-specific usage of this functionality is to adjust GPU
   priority for groups of processes.  Based on Chris' feedback, I've
   made this control a "priority offset" rather than just a starting
   priority, so that the change applied by cgroup will be added to the
   explicitly-set context priority rather than being overwritten by it.
   At the moment i915 still just assigns the priority offset one time at
   context creation and doesn't alter it if the process migrates between
   cgroups at runtime or if the cgroup has a new value assigned to it;
   such changes only affect the priority offset of new contexts created
   by a process.  I'm open to feedback on whether we should also make
   cgroup changes affect existing GPU context(s) from a process.

As noted on v1 of my patch series, cgroup control of graphics driver
concepts is expected to be done mostly during system startup (e.g., a
sysv-init script or a systemd recipe written by a system integrator and
custom to their own setup), so we don't really need a terribly
complicated userspace, just a simple tool that can be called by
appropriate scripts/recipes to set the desired policy.  I've re-written
the tool from v1 of the patch series as an i-g-t tool this time and will
send it as followup email shortly.

Still on my TODO list (once I gather some more general feedback and move
out of the early RFC stage):
 * Document this more fully in both the cgroups documentation and the
   i915 kerneldoc.
 * Write some i-g-t tests to exercise the ioctl and all the corner
   cases.


Matt Roper (7):
  cgroup: Allow drivers to store data associated with a cgroup
  kernfs: Export kernfs_get_inode
  cgroup: Add interface to allow drivers to lookup process cgroup
    membership
  drm: Add helper to obtain cgroup of drm_file's owning process
  drm/i915: cgroup integration
  drm/i915: Introduce 'priority offset' for GPU contexts
  drm/i915: Add context priority & priority offset to debugfs

 drivers/gpu/drm/i915/Kconfig            |   1 +
 drivers/gpu/drm/i915/Makefile           |   1 +
 drivers/gpu/drm/i915/i915_cgroup.c      | 180 ++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_debugfs.c     |   3 +
 drivers/gpu/drm/i915/i915_drv.c         |   7 ++
 drivers/gpu/drm/i915/i915_drv.h         |  31 ++++++
 drivers/gpu/drm/i915/i915_gem_context.c |   6 +-
 drivers/gpu/drm/i915/i915_gem_context.h |   9 ++
 fs/kernfs/inode.c                       |   1 +
 include/drm/drm_file.h                  |  20 ++++
 include/linux/cgroup-defs.h             |  37 +++++++
 include/linux/cgroup.h                  |  33 ++++++
 include/uapi/drm/i915_drm.h             |  13 +++
 init/Kconfig                            |   4 +
 kernel/cgroup/Makefile                  |   1 +
 kernel/cgroup/cgroup.c                  |   1 +
 kernel/cgroup/cgroup_driver.c           | 162 ++++++++++++++++++++++++++++
 17 files changed, 508 insertions(+), 2 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/i915_cgroup.c
 create mode 100644 kernel/cgroup/cgroup_driver.c

-- 
2.14.3

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