[PATCH v3 4/4] drm/xe: Implement clear VRAM on free
Matthew Brost
matthew.brost at intel.com
Mon Jul 14 23:44:38 UTC 2025
On Fri, Jul 04, 2025 at 10:17:24AM +0100, Matthew Auld wrote:
> On 23/06/2025 16:19, Matthew Brost wrote:
> > Clearing on free should hide latency of BO clears on new user BO
> > allocations.
> >
> > Implemented via calling xe_migrate_clear in release notify and updating
> > iterator in xe_migrate_clear to skip cleared buddy blocks. Only user BOs
> > cleared in release notify as kernel BOs could still be in use (e.g., PT
> > BOs need to wait for dma-resv to be idle).
> >
> > v2:
> > - Update to new xe_migrate_clear arguments (Thomas)
> > - Wait on BOOKKEEP slots for clear onn free (Thomas)
> > - s/XE_MIGRATE_CLEAR_NON_DIRTY/XE_MIGRATE_CLEAR_FLAG_ON_FREE
> > - Do not requested clear memory in VRAM manager if BO as TT data (Auld)
> >
> > Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> > ---
> > drivers/gpu/drm/xe/xe_bo.c | 48 ++++++++++++++++++++++++++++
> > drivers/gpu/drm/xe/xe_migrate.c | 31 ++++++++++++------
> > drivers/gpu/drm/xe/xe_migrate.h | 1 +
> > drivers/gpu/drm/xe/xe_res_cursor.h | 26 +++++++++++++++
> > drivers/gpu/drm/xe/xe_ttm_vram_mgr.c | 6 +++-
> > drivers/gpu/drm/xe/xe_ttm_vram_mgr.h | 6 ++++
> > 6 files changed, 108 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> > index 7a412121477e..900f67deef9d 100644
> > --- a/drivers/gpu/drm/xe/xe_bo.c
> > +++ b/drivers/gpu/drm/xe/xe_bo.c
> > @@ -1453,6 +1453,52 @@ static bool xe_ttm_bo_lock_in_destructor(struct ttm_buffer_object *ttm_bo)
> > return locked;
> > }
> > +static void xe_ttm_bo_release_clear(struct ttm_buffer_object *ttm_bo)
> > +{
> > + struct xe_device *xe = ttm_to_xe_device(ttm_bo->bdev);
> > + struct xe_bo *bo = ttm_to_xe_bo(ttm_bo);
> > + struct dma_fence *fence;
> > + int err, idx;
> > +
> > + xe_bo_assert_held(ttm_to_xe_bo(ttm_bo));
> > +
> > + if (ttm_bo->type != ttm_bo_type_device)
> > + return;
> > +
> > + if (xe_device_wedged(xe))
> > + return;
> > +
> > + if (!ttm_bo->resource || !mem_type_is_vram(ttm_bo->resource->mem_type))
> > + return;
> > +
> > + if (!drm_dev_enter(&xe->drm, &idx))
> > + return;
> > +
> > + if (!xe_pm_runtime_get_if_active(xe))
> > + goto unbind;
> > +
> > + err = dma_resv_reserve_fences(&ttm_bo->base._resv, 1);
> > + if (err)
> > + goto put_pm;
> > +
> > + fence = xe_migrate_clear(mem_type_to_migrate(xe, ttm_bo->resource->mem_type),
> > + ttm_bo->resource, &ttm_bo->base._resv, NULL,
> > + bo->size, XE_MIGRATE_CLEAR_FLAG_FULL |
> > + XE_MIGRATE_CLEAR_FLAG_ON_FREE, &bo->ccs_cleared);
> > + if (XE_WARN_ON(IS_ERR(fence)))
>
> Should we chuck a warn for this? I think there might be some intr waits in
> there which could legit trigger?
>
Unless I'm missing something, nothing xe_migrate_clear in interruptable.
All the locks are non-interruptable, same with waits. Also this should
be a kernel contetxt, not interrutable user context, right?
> > + goto put_pm;
> > +
> > + xe_ttm_vram_mgr_resource_set_cleared(ttm_bo->resource);
> > + dma_resv_add_fence(&ttm_bo->base._resv, fence,
> > + DMA_RESV_USAGE_KERNEL);
> > + dma_fence_put(fence);
> > +
> > +put_pm:
> > + xe_pm_runtime_put(xe);
> > +unbind:
> > + drm_dev_exit(idx);
> > +}
> > +
> > static void xe_ttm_bo_release_notify(struct ttm_buffer_object *ttm_bo)
> > {
> > struct dma_resv_iter cursor;
> > @@ -1497,6 +1543,8 @@ static void xe_ttm_bo_release_notify(struct ttm_buffer_object *ttm_bo)
> > }
> > dma_fence_put(replacement);
> > + xe_ttm_bo_release_clear(ttm_bo);
> > +
> > dma_resv_unlock(ttm_bo->base.resv);
> > }
> > diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
> > index 18030f9613ae..7620f4eb8fb3 100644
> > --- a/drivers/gpu/drm/xe/xe_migrate.c
> > +++ b/drivers/gpu/drm/xe/xe_migrate.c
> > @@ -1067,7 +1067,7 @@ struct dma_fence *xe_migrate_clear(struct xe_migrate *m,
> > struct xe_gt *gt = m->tile->primary_gt;
> > struct xe_device *xe = gt_to_xe(gt);
> > bool clear_only_system_ccs = false;
> > - struct dma_fence *fence = NULL;
> > + struct dma_fence *fence = dma_fence_get_stub();
> > struct xe_res_cursor src_it;
> > struct ttm_resource *src = dst;
> > int err;
> > @@ -1078,10 +1078,13 @@ struct dma_fence *xe_migrate_clear(struct xe_migrate *m,
> > if (!clear_bo_data && clear_ccs && !IS_DGFX(xe))
> > clear_only_system_ccs = true;
> > - if (!clear_vram)
> > + if (!clear_vram) {
> > xe_res_first_sg(sgt, 0, size, &src_it);
> > - else
> > + } else {
> > xe_res_first(src, 0, size, &src_it);
> > + if (!(clear_flags & XE_MIGRATE_CLEAR_FLAG_ON_FREE))
> > + size -= xe_res_next_dirty(&src_it);
> > + }
> > while (size) {
> > u64 clear_L0_ofs;
> > @@ -1128,6 +1131,9 @@ struct dma_fence *xe_migrate_clear(struct xe_migrate *m,
> > emit_pte(m, bb, clear_L0_pt, clear_vram, clear_only_system_ccs,
> > &src_it, clear_L0, dst);
> > + if (clear_vram && !(clear_flags & XE_MIGRATE_CLEAR_FLAG_ON_FREE))
> > + size -= xe_res_next_dirty(&src_it);
> > +
> > bb->cs[bb->len++] = MI_BATCH_BUFFER_END;
> > update_idx = bb->len;
> > @@ -1149,15 +1155,22 @@ struct dma_fence *xe_migrate_clear(struct xe_migrate *m,
> > }
> > xe_sched_job_add_migrate_flush(job, flush_flags);
> > - if (!fence) {
> > + if (fence == dma_fence_get_stub()) {
>
> Does this get() always have a matching put()? Say fence != stub?
>
Maybe not, but I think that is ok given you don't want a dma-fence to be
destroyed. This is a bit of backwwards checkout though as
dma_fence_get_stub takes a spin_lock and increments a ref count. Let me
rework this a bit.
Matt
> > + enum dma_resv_usage usage =
> > + (clear_flags & XE_MIGRATE_CLEAR_FLAG_ON_FREE) ?
> > + DMA_RESV_USAGE_BOOKKEEP : DMA_RESV_USAGE_KERNEL;
> > +
> > /*
> > - * There can't be anything userspace related at this
> > - * point, so we just need to respect any potential move
> > - * fences, which are always tracked as
> > + * For initial clears, there can't be anything userspace
> > + * related at this point, so we just need to respect any
> > + * potential move fences, which are always tracked as
> > * DMA_RESV_USAGE_KERNEL.
> > + *
> > + * For clear on free need to respect all fences as
> > + * memory could still be in use by the GPU which is
> > + * tracked in DMA_RESV_USAGE_BOOKKEEP.
> > */
> > - err = xe_sched_job_add_deps(job, resv,
> > - DMA_RESV_USAGE_KERNEL);
> > + err = xe_sched_job_add_deps(job, resv, usage);
> > if (err)
> > goto err_job;
> > }
> > diff --git a/drivers/gpu/drm/xe/xe_migrate.h b/drivers/gpu/drm/xe/xe_migrate.h
> > index 04b3cd86ba90..104c61812ba1 100644
> > --- a/drivers/gpu/drm/xe/xe_migrate.h
> > +++ b/drivers/gpu/drm/xe/xe_migrate.h
> > @@ -120,6 +120,7 @@ int xe_migrate_access_memory(struct xe_migrate *m, struct xe_bo *bo,
> > #define XE_MIGRATE_CLEAR_FLAG_BO_DATA BIT(0)
> > #define XE_MIGRATE_CLEAR_FLAG_CCS_DATA BIT(1)
> > +#define XE_MIGRATE_CLEAR_FLAG_ON_FREE BIT(2)
> > #define XE_MIGRATE_CLEAR_FLAG_FULL (XE_MIGRATE_CLEAR_FLAG_BO_DATA | \
> > XE_MIGRATE_CLEAR_FLAG_CCS_DATA)
> > struct dma_fence *xe_migrate_clear(struct xe_migrate *m,
> > diff --git a/drivers/gpu/drm/xe/xe_res_cursor.h b/drivers/gpu/drm/xe/xe_res_cursor.h
> > index d1a403cfb628..630082e809ba 100644
> > --- a/drivers/gpu/drm/xe/xe_res_cursor.h
> > +++ b/drivers/gpu/drm/xe/xe_res_cursor.h
> > @@ -315,6 +315,32 @@ static inline void xe_res_next(struct xe_res_cursor *cur, u64 size)
> > }
> > }
> > +/**
> > + * xe_res_next_dirty - advance the cursor to next dirty buddy block
> > + *
> > + * @cur: the cursor to advance
> > + *
> > + * Move the cursor until dirty buddy block is found.
> > + *
> > + * Return: Number of bytes cursor has been advanced
> > + */
> > +static inline u64 xe_res_next_dirty(struct xe_res_cursor *cur)
> > +{
> > + struct drm_buddy_block *block = cur->node;
> > + u64 bytes = 0;
> > +
> > + XE_WARN_ON(cur->mem_type != XE_PL_VRAM0 &&
> > + cur->mem_type != XE_PL_VRAM1);
> > +
> > + while (cur->remaining && drm_buddy_block_is_clear(block)) {
> > + bytes += cur->size;
> > + xe_res_next(cur, cur->size);
> > + block = cur->node;
> > + }
> > +
> > + return bytes;
> > +}
> > +
> > /**
> > * xe_res_dma - return dma address of cursor at current position
> > *
> > diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
> > index 9e375a40aee9..838739e47815 100644
> > --- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
> > +++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
> > @@ -84,6 +84,10 @@ static int xe_ttm_vram_mgr_new(struct ttm_resource_manager *man,
> > if (place->fpfn || lpfn != man->size >> PAGE_SHIFT)
> > vres->flags |= DRM_BUDDY_RANGE_ALLOCATION;
> > + if (tbo->type == ttm_bo_type_device &&
> > + !xe_bo_tt_has_data(ttm_to_xe_bo(tbo)))
> > + vres->flags |= DRM_BUDDY_CLEAR_ALLOCATION;
> > +
> > if (WARN_ON(!vres->base.size)) {
> > err = -EINVAL;
> > goto error_fini;
> > @@ -187,7 +191,7 @@ static void xe_ttm_vram_mgr_del(struct ttm_resource_manager *man,
> > struct drm_buddy *mm = &mgr->mm;
> > mutex_lock(&mgr->lock);
> > - drm_buddy_free_list(mm, &vres->blocks, 0);
> > + drm_buddy_free_list(mm, &vres->blocks, vres->flags);
> > mgr->visible_avail += vres->used_visible_size;
> > mutex_unlock(&mgr->lock);
> > diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h
> > index cc76050e376d..dfc0e6890b3c 100644
> > --- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h
> > +++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.h
> > @@ -36,6 +36,12 @@ to_xe_ttm_vram_mgr_resource(struct ttm_resource *res)
> > return container_of(res, struct xe_ttm_vram_mgr_resource, base);
> > }
> > +static inline void
> > +xe_ttm_vram_mgr_resource_set_cleared(struct ttm_resource *res)
> > +{
> > + to_xe_ttm_vram_mgr_resource(res)->flags |= DRM_BUDDY_CLEARED;
> > +}
> > +
> > static inline struct xe_ttm_vram_mgr *
> > to_xe_ttm_vram_mgr(struct ttm_resource_manager *man)
> > {
>
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