[v16,0/7] TTM shrinker helpers and xe buffer object shrinker

Message

Thomas Hellström Jan. 30, 2025, 10:13 a.m. UTC

This series implements TTM shrinker / eviction helpers and an xe bo
shrinker. It builds on a previous series, *and obsoletes that one*.

https://lore.kernel.org/linux-mm/[e-mail]/T/

Where the comment about layering
https://lore.kernel.org/linux-mm/[e-mail]/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.

The series earlier consisted of a LRU traversal part and the current part.
The LRU traversal part is merged, but is still mentioned in the history
below.

Patch 1 introduces a backup implemententaion.

Patch 2 introduces functionality 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.

Patch 3 Adds a simple error injection to the above code to help increase
test coverage.

Patch 4 Implements a macro for LRU iteration.

Patch 5 Introduces driver-facing helpers for shrinking.

Patch 6 Implements the xe bo shrinker.

Patch 7 Increases (removes) the XE_PL_TT watermark.

v2:
- Squash obsolete revision history in the patch commit messages.
- Fix a couple of review comments by Christian
- Don't store the mem_type in the TTM managers but in the
  resource cursor.
- Rename introduced TTM *back_up* function names to *backup*
- Add ttm pool recovery fault injection.
- Shrinker xe kunit test
- Various bugfixes

v3:
- Address some review comments from Matthew Brost and Christian König.
- Use the restartable LRU walk for TTM swapping and eviction.
- Provide a POC drm_exec locking implementation for exhaustive
  eviction. (Christian König).

v4:
- Remove the RFC exhaustive eviction part. While the path to exhaustive
  eviction is pretty clear and demonstrated in v3, there is still some
  drm_exec work that needs to be agreed and implemented.
- Add shrinker power management. On some hw we need to wake when shrinking.
- Fix the lru walker helper for -EALREADY errors.
- Add drm/xe: Increase the XE_PL_TT watermark.

v5:
- Update also TTM kunit tests
- Handle ghost- and zombie objects in the shrinker.
- A couple of compile- and UAF fixes reported by Kernel Build Robot and
  Dan Carpenter.

v6:
- Address review comments from Matthew Brost on the
  restartable LRU traversal path.

v7:
- Split out TTM restartable LRU traversal path and merge that.
- Adapt the review comments on that series.

v8:
- Address review comments from Matthew Brost as detailed in the
  respective patches.

v9:
- Rebase and fix compilation errors

v10:
- Use a LRU iteration macro rather than a function with a callback.
- Rebasing and cleanups
- Address some additional review comments from Matt Brost.
- Drop the shrinker selftest. It was already merged as a swapout
  self-test.

v11:
- Move more core interaction to additional TTM helpers.
- Don't back up without __GFP_FS, and don't start writeback without __GFP_IO.
- Rebase.

v12:
- Fix an indentation flaw.
- Rebase

v13:
- Remove the backup base-class, and use direct calls for ttm_backup
  (Christian König).
- Rebase on the ttm_backup changes.
- Move shrunken bos from the LRU list to the unevictable list.
- Provide an accessor function with sanity checks to set the
- ttm_tt::backup field.
- Update documentation.

v14:
- Update documentation of ttm_backup_bytes_avail().
- Work around converting between struct file * and struct ttm-backup *.
- Don't set up backup for imported buffers.

v15:
- ttm_backup return value change. (Christian König)
- ttm_pool restore/alloc implementation rework (Christian König)
- Documentation update.
- Remove cond_resched (Christian König)

v16:
- Two patches merged. Rebase.

Cc: Christian König <[e-mail]>
Cc: Matthew Brost <[e-mail]>
Cc: Paulo Zanoni <[e-mail]>
Cc: <[e-mail]>

Thomas Hellström (7):
  drm/ttm: Provide a shmem backup implementation
  drm/ttm/pool, drm/ttm/tt: Provide a helper to shrink pages
  drm/ttm: Use fault-injection to test error paths
  drm/ttm: Add a macro to perform LRU iteration
  drm/ttm: Add helpers for shrinking
  drm/xe: Add a shrinker for xe bos
  drm/xe: Increase the XE_PL_TT watermark

 drivers/gpu/drm/ttm/Makefile         |   2 +-
 drivers/gpu/drm/ttm/ttm_backup.c     | 207 ++++++++++
 drivers/gpu/drm/ttm/ttm_bo_util.c    | 247 +++++++++++-
 drivers/gpu/drm/ttm/ttm_pool.c       | 577 ++++++++++++++++++++++++---
 drivers/gpu/drm/ttm/ttm_tt.c         |  83 ++++
 drivers/gpu/drm/xe/Makefile          |   1 +
 drivers/gpu/drm/xe/tests/xe_bo.c     |   6 +-
 drivers/gpu/drm/xe/xe_bo.c           | 202 +++++++++-
 drivers/gpu/drm/xe/xe_bo.h           |  36 ++
 drivers/gpu/drm/xe/xe_device.c       |   8 +
 drivers/gpu/drm/xe/xe_device_types.h |   2 +
 drivers/gpu/drm/xe/xe_shrinker.c     | 258 ++++++++++++
 drivers/gpu/drm/xe/xe_shrinker.h     |  18 +
 drivers/gpu/drm/xe/xe_ttm_sys_mgr.c  |   3 +-
 include/drm/ttm/ttm_backup.h         |  74 ++++
 include/drm/ttm/ttm_bo.h             |  93 +++++
 include/drm/ttm/ttm_pool.h           |   8 +
 include/drm/ttm/ttm_tt.h             |  69 +++-
 18 files changed, 1814 insertions(+), 80 deletions(-)
 create mode 100644 drivers/gpu/drm/ttm/ttm_backup.c
 create mode 100644 drivers/gpu/drm/xe/xe_shrinker.c
 create mode 100644 drivers/gpu/drm/xe/xe_shrinker.h
 create mode 100644 include/drm/ttm/ttm_backup.h