[RFC PATCH 0/8] TTM shrinker helpers and xe buffer object shrinker

[Thomas Hellström]

This series implements TTM shrinker / eviction helpers and an xe bo
shrinker. It builds on two previous series. First

https://www.mail-archive.com/dri-devel@lists.freedesktop.org/msg484425.html

for patch 1-4, which IMO still could be reviewed and pushed as a
separate series.

Second the previous TTM shrinker series

https://lore.kernel.org/linux-mm/b7491378-defd-4f1c-31e2-29e4c77e2d67@amd.com/T/

Where the comment about layering
https://lore.kernel.org/linux-mm/b7491378-defd-4f1c-31e2-29e4c77e2d67@amd.com/T/#ma918844aa8a6efe8768fdcda0c6590d5c93850c9

now addressed, and this version also implements shmem objects for backup
rather than direct swap-cache insertions, which was used in the previuos
series. It turns out that with per-page backup / shrinking, shmem objects
appears to work just as well as direct swap-cache insertions with the
added benefit that was introduced in the previous TTM shrinker series to
avoid running out of swap entries isn't really needed.

In any case, patch 1-4 are better described in their separate series.
(RFC is removed for those).

Patch 5 could in theory be skipped but introduces a possibility to easily
add or test multiple backup backends, like the direct swap-cache
insertion or even files into fast dedicated nvme storage for for example.

Patch 6 introduces helpers in the ttm_pool code for page-by-page shrinking
and recovery. It avoids having to temporarily allocate a huge amount of
memory to be able to shrink a buffer object. It also introduces the
possibility to immediately write-back pages if needed, since that tends
to be a bit delayed when left to kswapd.

Patch 7 introduces a LRU walk helper for eviction and shrinking. It's
currently xe-only but not xe-specific and can easily be moved to TTM when
used by more than one driver or when eviction is implemented using it.

Patch 8 introduces a helper callback for shrinking (Also ready to be
moved to TTM) and an xe-specific shrinker implementation.

Testing:
ATM I don't think we have good tests to cover the shrinking functionality
The series has been tested with a hack that continously creates
TTM_TT buffer objects until system memory and swap space is exhausted,
and then reads them back and frees them. However, these tests
seem to be very slow.
Ideally a similar test on a machine with very fast solid state or
similar storage should be set up. Ideally also verifying content
preservation.

Cc: Somalapuram Amaranath <Amaranath.Somalapuram at amd.com>
Cc: Christian König <christian.koenig at amd.com>
Cc: <dri-devel at lists.freedesktop.org>

Thomas Hellström (8):
  drm/ttm: Allow TTM LRU list nodes of different types
  drm/ttm: Use LRU hitches
  drm/ttm, drm/amdgpu, drm/xe: Consider hitch moves within bulk sublist
    moves
  drm/ttm: Allow continued swapout after -ENOSPC falure
  drm/ttm: Add a virtual base class for graphics memory backup
  drm/ttm/pool: Provide a helper to shrink pages.
  drm/xe, drm/ttm: Provide a generic LRU walker helper
  drm/xe: Add a shrinker for xe bos

 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c |   4 +
 drivers/gpu/drm/ttm/Makefile           |   2 +-
 drivers/gpu/drm/ttm/ttm_backup_shmem.c | 137 +++++++++
 drivers/gpu/drm/ttm/ttm_bo.c           |   1 +
 drivers/gpu/drm/ttm/ttm_device.c       |  33 ++-
 drivers/gpu/drm/ttm/ttm_pool.c         | 391 ++++++++++++++++++++++++-
 drivers/gpu/drm/ttm/ttm_resource.c     | 231 ++++++++++++---
 drivers/gpu/drm/ttm/ttm_tt.c           |  34 +++
 drivers/gpu/drm/xe/Makefile            |   2 +
 drivers/gpu/drm/xe/xe_bo.c             | 123 ++++++--
 drivers/gpu/drm/xe/xe_bo.h             |   3 +
 drivers/gpu/drm/xe/xe_device.c         |   8 +
 drivers/gpu/drm/xe/xe_device_types.h   |   2 +
 drivers/gpu/drm/xe/xe_shrinker.c       | 237 +++++++++++++++
 drivers/gpu/drm/xe/xe_shrinker.h       |  18 ++
 drivers/gpu/drm/xe/xe_ttm_helpers.c    | 224 ++++++++++++++
 drivers/gpu/drm/xe/xe_ttm_helpers.h    |  63 ++++
 drivers/gpu/drm/xe/xe_vm.c             |   4 +
 include/drm/ttm/ttm_backup.h           | 136 +++++++++
 include/drm/ttm/ttm_device.h           |   2 +
 include/drm/ttm/ttm_pool.h             |   4 +
 include/drm/ttm/ttm_resource.h         |  96 +++++-
 include/drm/ttm/ttm_tt.h               |  19 ++
 23 files changed, 1683 insertions(+), 91 deletions(-)
 create mode 100644 drivers/gpu/drm/ttm/ttm_backup_shmem.c
 create mode 100644 drivers/gpu/drm/xe/xe_shrinker.c
 create mode 100644 drivers/gpu/drm/xe/xe_shrinker.h
 create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.c
 create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.h
 create mode 100644 include/drm/ttm/ttm_backup.h

-- 
2.44.0