On Mon, 14 Jun 2021 at 11:32, Thomas Hellström
<thomas.hellstrom@xxxxxxxxxxxxxxx> wrote:
>
>
> On 6/14/21 12:20 PM, Matthew Auld wrote:
> > On Mon, 14 Jun 2021 at 10:53, Thomas Hellström
> > <thomas.hellstrom@xxxxxxxxxxxxxxx> wrote:
> >> After a TTM move or object init we need to update the i915 gem flags and
> >> caching settings to reflect the new placement. Currently caching settings
> >> are not changed during the lifetime of an object, although that might
> >> change moving forward if we run into performance issues or issues with
> >> WC system page allocations.
> >> Also introduce gpu_binds_iomem() and cpu_maps_iomem() to clean up the
> >> various ways we previously used to detect this.
> >> Finally, initialize the TTM object reserved to be able to update
> >> flags and caching before anyone else gets hold of the object.
> >>
> >> Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> >> ---
> >> v2:
> >> - Style fixes (Reported by Matthew Auld)
> >> v3:
> >> - More style fixes. Clarify why we're updating caching settings after move.
> >> (Suggested by Matthew Auld)
> >> ---
> >> drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 111 +++++++++++++++++++-----
> >> 1 file changed, 89 insertions(+), 22 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> >> index 33ab47f1e05b..5176682a7d19 100644
> >> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> >> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> >> @@ -70,6 +70,17 @@ static struct ttm_placement i915_sys_placement = {
> >> .busy_placement = &lmem0_sys_placement_flags[1],
> >> };
> >>
> >> +static bool gpu_binds_iomem(struct ttm_resource *mem)
> >> +{
> >> + return mem->mem_type != TTM_PL_SYSTEM;
> >> +}
> >> +
> >> +static bool cpu_maps_iomem(struct ttm_resource *mem)
> >> +{
> >> + /* Once / if we support GGTT, this is also false for cached ttm_tts */
> >> + return mem->mem_type != TTM_PL_SYSTEM;
> >> +}
> >> +
> >> static void i915_ttm_adjust_lru(struct drm_i915_gem_object *obj);
> >>
> >> static struct ttm_tt *i915_ttm_tt_create(struct ttm_buffer_object *bo,
> >> @@ -175,6 +186,40 @@ static void i915_ttm_free_cached_io_st(struct drm_i915_gem_object *obj)
> >> obj->ttm.cached_io_st = NULL;
> >> }
> >>
> >> +static void
> >> +i915_ttm_adjust_domains_after_cpu_move(struct drm_i915_gem_object *obj)
> >> +{
> >> + struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
> >> +
> >> + if (cpu_maps_iomem(bo->resource) || bo->ttm->caching != ttm_cached) {
> >> + obj->write_domain = I915_GEM_DOMAIN_WC;
> >> + obj->read_domains = I915_GEM_DOMAIN_WC;
> >> + } else {
> >> + obj->write_domain = I915_GEM_DOMAIN_CPU;
> >> + obj->read_domains = I915_GEM_DOMAIN_CPU;
> >> + }
> >> +}
> >> +
> >> +static void i915_ttm_adjust_gem_after_move(struct drm_i915_gem_object *obj)
> >> +{
> >> + struct drm_i915_private *i915 = to_i915(obj->base.dev);
> >> + struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
> >> + unsigned int cache_level;
> >> +
> >> + obj->mem_flags &= ~(I915_BO_FLAG_STRUCT_PAGE | I915_BO_FLAG_IOMEM);
> >> +
> >> + obj->mem_flags |= cpu_maps_iomem(bo->resource) ? I915_BO_FLAG_IOMEM :
> >> + I915_BO_FLAG_STRUCT_PAGE;
> >> +
> >> + if ((HAS_LLC(i915) || HAS_SNOOP(i915)) && !gpu_binds_iomem(bo->resource) &&
> >> + bo->ttm->caching == ttm_cached)
> >> + cache_level = I915_CACHE_LLC;
> >> + else
> >> + cache_level = I915_CACHE_NONE;
> >> +
> >> + i915_gem_object_set_cache_coherency(obj, cache_level);
> >> +}
> >> +
> >> static void i915_ttm_purge(struct drm_i915_gem_object *obj)
> >> {
> >> struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
> >> @@ -190,8 +235,10 @@ static void i915_ttm_purge(struct drm_i915_gem_object *obj)
> >>
> >> /* TTM's purge interface. Note that we might be reentering. */
> >> ret = ttm_bo_validate(bo, &place, &ctx);
> >> -
> >> if (!ret) {
> >> + obj->write_domain = 0;
> >> + obj->read_domains = 0;
> >> + i915_ttm_adjust_gem_after_move(obj);
> >> i915_ttm_free_cached_io_st(obj);
> >> obj->mm.madv = __I915_MADV_PURGED;
> >> }
> >> @@ -273,12 +320,15 @@ i915_ttm_resource_get_st(struct drm_i915_gem_object *obj,
> >> struct ttm_resource *res)
> >> {
> >> struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
> >> - struct ttm_resource_manager *man =
> >> - ttm_manager_type(bo->bdev, res->mem_type);
> >>
> >> - if (man->use_tt)
> >> + if (!gpu_binds_iomem(res))
> >> return i915_ttm_tt_get_st(bo->ttm);
> >>
> >> + /*
> >> + * If CPU mapping differs, we need to add the ttm_tt pages to
> >> + * the resulting st. Might make sense for GGTT.
> >> + */
> >> + GEM_WARN_ON(!cpu_maps_iomem(res));
> >> return intel_region_ttm_node_to_st(obj->mm.region, res);
> >> }
> >>
> >> @@ -290,8 +340,6 @@ static int i915_ttm_move(struct ttm_buffer_object *bo, bool evict,
> >> struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
> >> struct ttm_resource_manager *dst_man =
> >> ttm_manager_type(bo->bdev, dst_mem->mem_type);
> >> - struct ttm_resource_manager *src_man =
> >> - ttm_manager_type(bo->bdev, bo->resource->mem_type);
> >> struct intel_memory_region *dst_reg, *src_reg;
> >> union {
> >> struct ttm_kmap_iter_tt tt;
> >> @@ -332,34 +380,36 @@ static int i915_ttm_move(struct ttm_buffer_object *bo, bool evict,
> >> if (IS_ERR(dst_st))
> >> return PTR_ERR(dst_st);
> >>
> >> - /* If we start mapping GGTT, we can no longer use man::use_tt here. */
> >> - dst_iter = dst_man->use_tt ?
> >> + dst_iter = !cpu_maps_iomem(dst_mem) ?
> >> ttm_kmap_iter_tt_init(&_dst_iter.tt, bo->ttm) :
> >> ttm_kmap_iter_iomap_init(&_dst_iter.io, &dst_reg->iomap,
> >> dst_st, dst_reg->region.start);
> >>
> >> - src_iter = src_man->use_tt ?
> >> + src_iter = !cpu_maps_iomem(bo->resource) ?
> >> ttm_kmap_iter_tt_init(&_src_iter.tt, bo->ttm) :
> >> ttm_kmap_iter_iomap_init(&_src_iter.io, &src_reg->iomap,
> >> obj->ttm.cached_io_st,
> >> src_reg->region.start);
> >>
> >> ttm_move_memcpy(bo, dst_mem->num_pages, dst_iter, src_iter);
> >> + /* Below dst_mem becomes bo->resource. */
> >> ttm_bo_move_sync_cleanup(bo, dst_mem);
> >> + i915_ttm_adjust_domains_after_cpu_move(obj);
> >> i915_ttm_free_cached_io_st(obj);
> >>
> >> - if (!dst_man->use_tt) {
> >> + if (gpu_binds_iomem(dst_mem) || cpu_maps_iomem(dst_mem)) {
> >> obj->ttm.cached_io_st = dst_st;
> >> obj->ttm.get_io_page.sg_pos = dst_st->sgl;
> >> obj->ttm.get_io_page.sg_idx = 0;
> >> }
> >>
> >> + i915_ttm_adjust_gem_after_move(obj);
> >> return 0;
> >> }
> >>
> >> static int i915_ttm_io_mem_reserve(struct ttm_device *bdev, struct ttm_resource *mem)
> >> {
> >> - if (mem->mem_type < I915_PL_LMEM0)
> >> + if (!cpu_maps_iomem(mem))
> >> return 0;
> >>
> >> mem->bus.caching = ttm_write_combined;
> >> @@ -421,6 +471,16 @@ static int i915_ttm_get_pages(struct drm_i915_gem_object *obj)
> >> if (ret)
> >> return ret == -ENOSPC ? -ENXIO : ret;
> >>
> >> + i915_ttm_adjust_lru(obj);
> >> + if (bo->ttm && !ttm_tt_is_populated(bo->ttm)) {
> >> + ret = ttm_tt_populate(bo->bdev, bo->ttm, &ctx);
> >> + if (ret)
> >> + return ret;
> >> +
> >> + i915_ttm_adjust_domains_after_cpu_move(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))
> >> @@ -428,8 +488,6 @@ static int i915_ttm_get_pages(struct drm_i915_gem_object *obj)
> >>
> >> __i915_gem_object_set_pages(obj, st, i915_sg_dma_sizes(st->sgl));
> >>
> >> - i915_ttm_adjust_lru(obj);
> >> -
> >> return ret;
> >> }
> >>
> >> @@ -563,6 +621,7 @@ static u64 i915_ttm_mmap_offset(struct drm_i915_gem_object *obj)
> >>
> >> const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = {
> >> .name = "i915_gem_object_ttm",
> >> + .flags = I915_GEM_OBJECT_IS_SHRINKABLE,
> > We set is_shrinkable for both lmem and smem? Does the current shrinker
> > work with !shmem? I assume the put_pages() will just discard the page
> > contents, which is not what we want? Maybe keep this disabled for now?
> > Or am I missing something?
>
> This is to indicate to the gem shrinker that we want to be able to
> determine dynamically whether the object is shrinkable (by the gem
> shrinker) or not. (See below). It's intended for the situation where we
> might want to use shmem to back cached-only ttm objects, and use our own
> shrinker.
>
> But if you think it's better, we could flip that ops flag once we
> actually have anything shrinkable in place. Let me know what you think.
> The TTM shmem pool idea becomes a bit doubtful by the fact that
> allocating some 8GB of system objects, populating and clearing them
> appears to be some 6X faster with a straightforward alloc approach (like
> TTM or the "internal" backend) than with shmem...
I would vote for keeping it turned off for now.
>
> >> .get_pages = i915_ttm_get_pages,
> >> .put_pages = i915_ttm_put_pages,
> >> @@ -599,6 +658,10 @@ int __i915_gem_ttm_object_init(struct intel_memory_region *mem,
> >> {
> >> static struct lock_class_key lock_class;
> >> struct drm_i915_private *i915 = mem->i915;
> >> + struct ttm_operation_ctx ctx = {
> >> + .interruptible = true,
> >> + .no_wait_gpu = false,
> >> + };
> >> enum ttm_bo_type bo_type;
> >> size_t alignment = 0;
> >> int ret;
> >> @@ -618,15 +681,14 @@ int __i915_gem_ttm_object_init(struct intel_memory_region *mem,
> >> i915_gem_object_init(obj, &i915_gem_ttm_obj_ops, &lock_class, flags);
> >> i915_gem_object_init_memory_region(obj, mem);
> >> i915_gem_object_make_unshrinkable(obj);
>
> Here we set the object to unshrinkable.
Oh, I totally missed that. But I don't think we are meant to call that
here, especially with IS_SHRINKABLE, since object_set_pages will later
make it shrinkable anyway, which looks like fun and games.
>
> /Thomas
>
>
