[PATCH v2 00/33] drm/ttm, drm/xe: Minimize dma-resv hold times and defragment sub-optimally backed BOs

[Matthew Brost]

The overarching goal of this series is to keep user-facing IOCTLs snappy
by holding the BO dma-resv lock for the shortest possible time, and to
push the expensive, best-effort work - page (re)allocation, DMA mapping
and placement fixups - into the background or out of the locked critical
section entirely.

Two related mechanisms fall out of that goal:

 - Out-of-lock backing. Page allocation and DMA mapping are the dominant
   cost of gem_create and of BO moves, and doing them under the dma-resv
   lock serializes otherwise-independent clients. This series preallocates
   the backing pages (and, where applicable, builds the DMA/IOVA mapping)
   outside the lock, then transfers the result into the BO under a brief
   lock hold. The user gets a fast IOCTL return; the heavy lifting happens
   without contending the reservation.

 - Page defragmentation. A BO allocated under memory pressure keeps its
   scattered, sub-optimally-ordered backing for its entire lifetime,
   costing TLB efficiency forever. TTM grows the plumbing to track
   order-failure and to re-back a populated BO in place at the beneficial
   order, and Xe wires up a background delayed worker that promotes such
   BOs on the GPU once memory is available again - again, off the hot
   path and without stalling the submitting thread.

Since v1 [1] the series has grown considerably. The bulk of the new
material is a direct result of profiling: once the defragmenter was in
place, the remaining dma-resv hold times and the per-BO
allocation/mapping costs showed up clearly, which motivated the
out-of-lock preallocation, the IOVA-based mapping path, and the amdgpu
counterpart. Rather than land the defragmenter alone, v2 folds in these
optimizations since they share the same infrastructure and the same
"hold dma-resv briefly, fix up in the background" architecture.

The series is organized in sections rather than described patch by patch:

 - Patches 1-10 (drm/ttm): core TTM preparation - order-failure tracking,
   the defragmentation move, reclaim backoff, and out-of-lock page
   preallocation plumbing.
 - Patches 11-14: other dependent drm/gpusvm and drm/xe patches this
   series builds on (DMA-mapping accounting, per-order DMA stats, async
   L2 flush, and a VM-teardown ordering fix).
 - Patches 15-23 (drm/xe): the page defragmenter itself - BO tracking,
   the on-GPU defrag copy, xe_bo_move() handling, and the background
   worker with its stats and configuration.
 - Patches 24-25 (drm/xe): out-of-lock system BO backing preallocation
   in gem_create, moving page allocation out of the dma-resv lock.
 - Patches 26-32 (drm/xe): IOVA-based DMA mapping optimizations, building
   and finalizing the mapping outside the lock.
 - Patch 33 (drm/amdgpu): the equivalent out-of-lock system BO
   preallocation for amdgpu, exercising the shared TTM plumbing.

Testing
=======

 - 3D benchmarks on Ubuntu and on Android, with memory intentionally
   fragmented by a separate program at launch (plus beneficial-order
   error injection). BOs are initially backed at a sub-optimal order and
   scores start lower; the background defrag worker then promotes the
   backing to the beneficial order and scores climb back in line with the
   unfragmented baseline.
 - IGT:
   https://patchwork.freedesktop.org/patch/739052/?series=170046&rev=2

Matt

[1] https://patchwork.freedesktop.org/series/169053/

Cc: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: Carlos Santa <carlos.santa@xxxxxxxxx>
Cc: Ryan Neph <ryanneph@xxxxxxxxxx>
Cc: Christian Koenig <christian.koenig@xxxxxxx>
Cc: Huang Rui <ray.huang@xxxxxxx>
Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Maxime Ripard <mripard@xxxxxxxxxx>
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: David Airlie <airlied@xxxxxxxxx>
Cc: Simona Vetter <simona@xxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>



Matthew Brost (31):
  drm/ttm/pool: Allow backing off reclaim at the beneficial order
  drm/ttm/pool: Add ttm_pool_page_order_nodma() helper
  drm/ttm: Record sub-optimal page order allocations in ttm_tt
  drm/ttm: Introduce ttm_pool_alloc_iter for __ttm_pool_alloc()
  drm/ttm: Support defragmentation moves
  drm/ttm: Add fault injection for beneficial-order allocation failures
  drm/ttm: Harvest beneficial-order pages on defragmentation moves
  drm/ttm: Bound page (re)allocation per defragmentation move
  drm/ttm: Preallocate beneficial-order defrag pages outside the lock
  drm/ttm: Add full out-of-lock preallocation for ttm_pool_alloc()
  drm/xe: Flush L2 asynchronously in xe_bo_trigger_rebind()
  drm/xe: Destroy page tables after unlinking all VMAs on VM close
  drm/xe: Track BOs backed at a sub-optimal page order
  drm/xe: Back off beneficial-order reclaim under defrag pressure
  drm/xe: Add xe_migrate_copy_defrag() for on-GPU defrag copies
  drm/xe: Handle defrag moves in xe_bo_move()
  drm/xe: Skip self-copies for borrowed pages on defrag moves
  drm/xe: Add a page defragmentation worker
  drm/xe: Add defrag GT stats
  drm/xe: Add Kconfig.profile options for BO defrag configuration
  drm/xe: Defrag using out-of-lock page preallocation
  drm/xe: Add defrag profiling tracepoints
  drm/xe: Preallocate system BO backing outside the dma-resv lock
  drm/xe: Add tracepoint for xe_gem_create_ioctl
  drm/xe: Add IOVA-based xe_res_cursor variant
  drm/xe: Use IOVA-based DMA mapping for eligible tt BOs
  drm/xe: Add per-device dependency scheduler for IOVA defrag finalize
  drm/xe: Add packed copy-step IOVA mapping for defrag
  drm/xe: Blit src-natural to dst-packed for defrag-IOVA copies
  drm/xe: Finalize defrag-IOVA moves with post-copy job
  drm/amdgpu: Preallocate system BO pages outside the reservation lock

Thomas Hellström (2):
  drm/gpusvm: Add a DMA-mapping accounting callback
  drm/xe: Add debugfs stats for DMA-mapped pages per order

 .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c  |    4 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c   |    2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c       |   45 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_gem.h       |    5 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_object.c    |    3 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_object.h    |    4 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c       |   39 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h       |    3 +
 drivers/gpu/drm/drm_gpusvm.c                  |   17 +-
 drivers/gpu/drm/ttm/ttm_bo.c                  |  101 +-
 drivers/gpu/drm/ttm/ttm_bo_util.c             |   21 +-
 drivers/gpu/drm/ttm/ttm_pool.c                |  931 +++++++++-
 drivers/gpu/drm/ttm/ttm_tt.c                  |   67 +
 drivers/gpu/drm/xe/Kconfig.profile            |   40 +
 drivers/gpu/drm/xe/tests/xe_bo.c              |    8 +-
 drivers/gpu/drm/xe/tests/xe_dma_buf.c         |    2 +-
 drivers/gpu/drm/xe/tests/xe_migrate.c         |   12 +-
 drivers/gpu/drm/xe/xe_bo.c                    | 1632 ++++++++++++++++-
 drivers/gpu/drm/xe/xe_bo.h                    |   15 +-
 drivers/gpu/drm/xe/xe_bo_types.h              |    6 +
 drivers/gpu/drm/xe/xe_debugfs.c               |   26 +
 drivers/gpu/drm/xe/xe_device.c                |   35 +
 drivers/gpu/drm/xe/xe_device_types.h          |   57 +
 drivers/gpu/drm/xe/xe_dma_buf.c               |    2 +-
 drivers/gpu/drm/xe/xe_ggtt.c                  |    2 +-
 drivers/gpu/drm/xe/xe_gt_stats.c              |    5 +
 drivers/gpu/drm/xe/xe_gt_stats_types.h        |   17 +
 drivers/gpu/drm/xe/xe_migrate.c               |  531 +++++-
 drivers/gpu/drm/xe/xe_migrate.h               |   17 +
 drivers/gpu/drm/xe/xe_pt.c                    |    2 +-
 drivers/gpu/drm/xe/xe_res_cursor.h            |   56 +-
 drivers/gpu/drm/xe/xe_svm.c                   |   36 +-
 drivers/gpu/drm/xe/xe_svm.h                   |    3 +-
 drivers/gpu/drm/xe/xe_trace_bo.h              |   90 +
 drivers/gpu/drm/xe/xe_userptr.c               |   55 +
 drivers/gpu/drm/xe/xe_userptr.h               |    1 +
 drivers/gpu/drm/xe/xe_vm.c                    |  149 +-
 drivers/gpu/drm/xe/xe_vm.h                    |    5 +
 include/drm/drm_gpusvm.h                      |   19 +
 include/drm/ttm/ttm_bo.h                      |   64 +
 include/drm/ttm/ttm_pool.h                    |   46 +
 include/drm/ttm/ttm_tt.h                      |   43 +-
 42 files changed, 4029 insertions(+), 189 deletions(-)

-- 
2.34.1