[Intel-gfx] [PATCH v3 1/5] drm/i915/gem: Implement object migration
Ruhl, Michael J
michael.j.ruhl at intel.com
Mon Jun 28 18:11:01 UTC 2021
>-----Original Message-----
>From: dri-devel <dri-devel-bounces at lists.freedesktop.org> On Behalf Of
>Thomas Hellström
>Sent: Monday, June 28, 2021 10:46 AM
>To: intel-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org
>Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>; Auld, Matthew
><matthew.auld at intel.com>; lkp <lkp at intel.com>
>Subject: [PATCH v3 1/5] drm/i915/gem: Implement object migration
>
>Introduce an interface to migrate objects between regions.
>This is primarily intended to migrate objects to LMEM for display and
>to SYSTEM for dma-buf, but might be reused in one form or another for
>performance-based migration.
>
>v2:
>- Verify that the memory region given as an id really exists.
> (Reported by Matthew Auld)
>- Call i915_gem_object_{init,release}_memory_region() when switching
>region
> to handle also switching region lists. (Reported by Matthew Auld)
>v3:
>- Fix i915_gem_object_can_migrate() to return true if object is already in
> the correct region, even if the object ops doesn't have a migrate()
> callback.
>- Update typo in commit message.
>- Fix kerneldoc of i915_gem_object_wait_migration().
>
>Reported-by: kernel test robot <lkp at intel.com>
>Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
>---
> drivers/gpu/drm/i915/gem/i915_gem_object.c | 96
>+++++++++++++++++++
> drivers/gpu/drm/i915/gem/i915_gem_object.h | 12 +++
> .../gpu/drm/i915/gem/i915_gem_object_types.h | 9 ++
> drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 69 +++++++++----
> drivers/gpu/drm/i915/gem/i915_gem_wait.c | 19 ++++
> 5 files changed, 188 insertions(+), 17 deletions(-)
>
>diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c
>b/drivers/gpu/drm/i915/gem/i915_gem_object.c
>index 07e8ff9a8aae..1c18be067b58 100644
>--- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
>+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
>@@ -513,6 +513,102 @@ bool i915_gem_object_has_iomem(const struct
>drm_i915_gem_object *obj)
> return obj->mem_flags & I915_BO_FLAG_IOMEM;
> }
>
>+/**
>+ * i915_gem_object_can_migrate - Whether an object likely can be migrated
>+ *
>+ * @obj: The object to migrate
>+ * @id: The region intended to migrate to
>+ *
>+ * Check whether the object backend supports migration to the
>+ * given region. Note that pinning may affect the ability to migrate.
>+ *
>+ * Return: true if migration is possible, false otherwise.
>+ */
>+bool i915_gem_object_can_migrate(struct drm_i915_gem_object *obj,
>+ enum intel_region_id id)
>+{
>+ struct drm_i915_private *i915 = to_i915(obj->base.dev);
>+ unsigned int num_allowed = obj->mm.n_placements;
>+ struct intel_memory_region *mr;
>+ unsigned int i;
>+
>+ GEM_BUG_ON(id >= INTEL_REGION_UNKNOWN);
>+ GEM_BUG_ON(obj->mm.madv != I915_MADV_WILLNEED);
>+
>+ mr = i915->mm.regions[id];
>+ if (!mr)
>+ return false;
>+
>+ if (obj->mm.region == mr)
>+ return true;
>+
>+ if (!i915_gem_object_evictable(obj))
>+ return false;
>+
>+ if (!obj->ops->migrate)
>+ return false;
>+
>+ if (!(obj->flags & I915_BO_ALLOC_USER))
>+ return true;
>+
>+ if (num_allowed == 0)
>+ return false;
>+
>+ for (i = 0; i < num_allowed; ++i) {
>+ if (mr == obj->mm.placements[i])
>+ return true;
>+ }
Hi Thomas,
I am a little confused over the difference in checks between this function
and i915_gem_object_migrate().
Why is the lack of an mr a BUG_ON in _object_migrate(), but here it just
false?
So that means that under certain circumstances, you could not have a mr?
If that is the case, when?
Would that be when the I915_BO_ALLOC_USER is set?
If so, should there be a check for "non" user vs user?
Or maybe document this function pointing out why there are differences
and why?
>+ return false;
>+}
>+
>+/**
>+ * i915_gem_object_migrate - Migrate an object to the desired region id
>+ * @obj: The object to migrate.
>+ * @ww: An optional struct i915_gem_ww_ctx. If NULL, the backend may
>+ * not be successful in evicting other objects to make room for this object.
Is the ww for future consideration? (I don't see any use of it in the patch).
>+ * @id: The region id to migrate to.
>+ *
>+ * Attempt to migrate the object to the desired memory region. The
>+ * object backend must support migration and the object may not be
>+ * pinned, (explicitly pinned pages or pinned vmas). The object must
>+ * be locked.
>+ * On successful completion, the object will have pages pointing to
>+ * memory in the new region, but an async migration task may not have
>+ * completed yet, and to accomplish that,
>i915_gem_object_wait_migration()
>+ * must be called.
>+ *
>+ * Return: 0 on success. Negative error code on failure. In particular may
>+ * return -ENXIO on lack of region space, -EDEADLK for deadlock avoidance
>+ * if @ww is set, -EINTR or -ERESTARTSYS if signal pending, and
>+ * -EBUSY if the object is pinned.
>+ */
>+int i915_gem_object_migrate(struct drm_i915_gem_object *obj,
>+ struct i915_gem_ww_ctx *ww,
>+ enum intel_region_id id)
>+{
>+ struct drm_i915_private *i915 = to_i915(obj->base.dev);
>+ struct intel_memory_region *mr;
>+
>+ GEM_BUG_ON(id >= INTEL_REGION_UNKNOWN);
>+ GEM_BUG_ON(obj->mm.madv != I915_MADV_WILLNEED);
>+ assert_object_held(obj);
>+
>+ mr = i915->mm.regions[id];
>+ GEM_BUG_ON(!mr);
>+
>+ if (obj->mm.region == mr)
>+ return 0;
>+
>+ if (!i915_gem_object_evictable(obj))
>+ return -EBUSY;
>+
>+ if (!obj->ops->migrate)
>+ return -EOPNOTSUPP;
Why aren't you using _can_migrate here?
>+ return obj->ops->migrate(obj, mr);
>+}
>+
> void i915_gem_init__objects(struct drm_i915_private *i915)
> {
> INIT_WORK(&i915->mm.free_work, __i915_gem_free_work);
>diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h
>b/drivers/gpu/drm/i915/gem/i915_gem_object.h
>index ea3224a480c4..8cbd7a5334e2 100644
>--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
>+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
>@@ -17,6 +17,8 @@
> #include "i915_gem_ww.h"
> #include "i915_vma_types.h"
>
>+enum intel_region_id;
>+
> /*
> * XXX: There is a prevalence of the assumption that we fit the
> * object's page count inside a 32bit _signed_ variable. Let's document
>@@ -597,6 +599,16 @@ bool i915_gem_object_migratable(struct
>drm_i915_gem_object *obj);
>
> bool i915_gem_object_validates_to_lmem(struct drm_i915_gem_object
>*obj);
>
>+int i915_gem_object_migrate(struct drm_i915_gem_object *obj,
>+ struct i915_gem_ww_ctx *ww,
>+ enum intel_region_id id);
>+
>+bool i915_gem_object_can_migrate(struct drm_i915_gem_object *obj,
>+ enum intel_region_id id);
>+
>+int i915_gem_object_wait_migration(struct drm_i915_gem_object *obj,
>+ unsigned int flags);
>+
> #ifdef CONFIG_MMU_NOTIFIER
> static inline bool
> i915_gem_object_is_userptr(struct drm_i915_gem_object *obj)
>diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
>b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
>index 441f913c87e6..ef3de2ae9723 100644
>--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
>+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
>@@ -18,6 +18,7 @@
>
> struct drm_i915_gem_object;
> struct intel_fronbuffer;
>+struct intel_memory_region;
>
> /*
> * struct i915_lut_handle tracks the fast lookups from handle to vma used
>@@ -77,6 +78,14 @@ struct drm_i915_gem_object_ops {
> * delayed_free - Override the default delayed free implementation
> */
> void (*delayed_free)(struct drm_i915_gem_object *obj);
>+
>+ /**
>+ * migrate - Migrate object to a different region either for
>+ * pinning or for as long as the object lock is held.
>+ */
>+ int (*migrate)(struct drm_i915_gem_object *obj,
>+ struct intel_memory_region *mr);
>+
> void (*release)(struct drm_i915_gem_object *obj);
>
> const struct vm_operations_struct *mmap_ops;
>diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>index c39d982c4fa6..8f89185b6507 100644
>--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
>@@ -617,7 +617,8 @@ struct ttm_device_funcs *i915_ttm_driver(void)
> return &i915_ttm_bo_driver;
> }
>
>-static int i915_ttm_get_pages(struct drm_i915_gem_object *obj)
>+static int __i915_ttm_get_pages(struct drm_i915_gem_object *obj,
>+ struct ttm_placement *placement)
> {
> struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
> struct ttm_operation_ctx ctx = {
>@@ -625,19 +626,12 @@ static int i915_ttm_get_pages(struct
>drm_i915_gem_object *obj)
> .no_wait_gpu = false,
> };
> struct sg_table *st;
>- struct ttm_place requested, busy[I915_TTM_MAX_PLACEMENTS];
>- struct ttm_placement placement;
> int real_num_busy;
> int ret;
>
>- GEM_BUG_ON(obj->mm.n_placements >
>I915_TTM_MAX_PLACEMENTS);
>-
>- /* Move to the requested placement. */
>- i915_ttm_placement_from_obj(obj, &requested, busy, &placement);
>-
> /* First try only the requested placement. No eviction. */
>- real_num_busy =
>fetch_and_zero(&placement.num_busy_placement);
>- ret = ttm_bo_validate(bo, &placement, &ctx);
>+ real_num_busy = fetch_and_zero(&placement-
>>num_busy_placement);
>+ ret = ttm_bo_validate(bo, placement, &ctx);
> if (ret) {
> ret = i915_ttm_err_to_gem(ret);
> /*
>@@ -652,8 +646,8 @@ static int i915_ttm_get_pages(struct
>drm_i915_gem_object *obj)
> * If the initial attempt fails, allow all accepted placements,
> * evicting if necessary.
> */
>- placement.num_busy_placement = real_num_busy;
>- ret = ttm_bo_validate(bo, &placement, &ctx);
>+ placement->num_busy_placement = real_num_busy;
>+ ret = ttm_bo_validate(bo, placement, &ctx);
> if (ret)
> return i915_ttm_err_to_gem(ret);
> }
>@@ -668,16 +662,56 @@ static int i915_ttm_get_pages(struct
>drm_i915_gem_object *obj)
> i915_ttm_adjust_gem_after_move(obj);
> }
>
>- /* Object either has a page vector or is an iomem object */
>- st = bo->ttm ? i915_ttm_tt_get_st(bo->ttm) : obj->ttm.cached_io_st;
>- if (IS_ERR(st))
>- return PTR_ERR(st);
>+ if (!obj->mm.pages) {
>+ /* Object either has a page vector or is an iomem object */
>+ st = bo->ttm ? i915_ttm_tt_get_st(bo->ttm) : obj-
>>ttm.cached_io_st;
>+ if (IS_ERR(st))
>+ return PTR_ERR(st);
>
>- __i915_gem_object_set_pages(obj, st, i915_sg_dma_sizes(st->sgl));
>+ __i915_gem_object_set_pages(obj, st,
>i915_sg_dma_sizes(st->sgl));
>+ }
>
> return ret;
> }
>
>+static int i915_ttm_get_pages(struct drm_i915_gem_object *obj)
>+{
>+ struct ttm_place requested, busy[I915_TTM_MAX_PLACEMENTS];
>+ struct ttm_placement placement;
>+
>+ GEM_BUG_ON(obj->mm.n_placements >
>I915_TTM_MAX_PLACEMENTS);
>+
>+ /* Move to the requested placement. */
>+ i915_ttm_placement_from_obj(obj, &requested, busy, &placement);
>+
>+ return __i915_ttm_get_pages(obj, &placement);
>+}
>+
>+static int i915_ttm_migrate(struct drm_i915_gem_object *obj,
>+ struct intel_memory_region *mr)
>+{
>+ struct ttm_place requested;
>+ struct ttm_placement placement;
>+ int ret;
>+
>+ i915_ttm_place_from_region(mr, &requested, obj->flags);
>+ placement.num_placement = 1;
>+ placement.num_busy_placement = 1;
>+ placement.placement = &requested;
>+ placement.busy_placement = &requested;
>+
>+ ret = __i915_ttm_get_pages(obj, &placement);
>+ if (ret)
>+ return ret;
>+
>+ if (obj->mm.region != mr) {
>+ i915_gem_object_release_memory_region(obj);
>+ i915_gem_object_init_memory_region(obj, mr);
>+ }
Perhaps a minor nit:
Doing this after we have done the _get_pages() just doesn't seem right.
I.e. we do work on the object, and then we init some portion of it.
Do we need to do this incase the migration/placement fails? If so,
maybe a comment to that effect?
Thanks,
Mike
>+ return 0;
>+}
>+
> static void i915_ttm_put_pages(struct drm_i915_gem_object *obj,
> struct sg_table *st)
> {
>@@ -814,6 +848,7 @@ static const struct drm_i915_gem_object_ops
>i915_gem_ttm_obj_ops = {
> .truncate = i915_ttm_purge,
> .adjust_lru = i915_ttm_adjust_lru,
> .delayed_free = i915_ttm_delayed_free,
>+ .migrate = i915_ttm_migrate,
> .mmap_offset = i915_ttm_mmap_offset,
> .mmap_ops = &vm_ops_ttm,
> };
>diff --git a/drivers/gpu/drm/i915/gem/i915_gem_wait.c
>b/drivers/gpu/drm/i915/gem/i915_gem_wait.c
>index 1070d3afdce7..f909aaa09d9c 100644
>--- a/drivers/gpu/drm/i915/gem/i915_gem_wait.c
>+++ b/drivers/gpu/drm/i915/gem/i915_gem_wait.c
>@@ -290,3 +290,22 @@ i915_gem_wait_ioctl(struct drm_device *dev, void
>*data, struct drm_file *file)
> i915_gem_object_put(obj);
> return ret;
> }
>+
>+/**
>+ * i915_gem_object_wait_migration - Sync an accelerated migration
>operation
>+ * @obj: The migrating object.
>+ * @flags: waiting flags. Currently supports only I915_WAIT_INTERRUPTIBLE.
>+ *
>+ * Wait for any pending async migration operation on the object,
>+ * whether it's explicitly (i915_gem_object_migrate()) or implicitly
>+ * (swapin, initial clearing) initiated.
>+ *
>+ * Return: 0 if successful, -ERESTARTSYS if a signal was hit during waiting.
>+ */
>+int i915_gem_object_wait_migration(struct drm_i915_gem_object *obj,
>+ unsigned int flags)
>+{
>+ might_sleep();
>+ /* NOP for now. */
>+ return 0;
>+}
>--
>2.31.1
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