On Mon, 2021-10-18 at 10:10 +0100, Matthew Auld wrote: > We currently just evict lmem objects to system memory when under > memory > pressure. For this case we might lack the usual object mm.pages, > which > effectively hides the pages from the i915-gem shrinker, until we > actually "attach" the TT to the object, or in the case of lmem-only > objects it just gets migrated back to lmem when touched again. > > For all cases we can just adjust the i915 shrinker LRU each time we > also > adjust the TTM LRU. The two cases we care about are: > > 1) When something is moved by TTM, including when initially > populating > an object. Importantly this covers the case where TTM moves > something from > lmem <-> smem, outside of the normal get_pages() interface, > which > should still ensure the shmem pages underneath are reclaimable. > > 2) When calling into i915_gem_object_unlock(). The unlock should > ensure the object is removed from the shinker LRU, if it was > indeed > swapped out, or just purged, when the shrinker drops the object > lock. > > v2(Thomas): > - Handle managing the shrinker LRU in adjust_lru, where it is > always > safe to touch the object. > v3(Thomas): > - Pretty much a re-write. This time piggy back off the shrink_pin > stuff, which actually seems to fit quite well for what we want > here. > v4(Thomas): > - Just use a simple boolean for tracking ttm_shrinkable. > v5: > - Ensure we call adjust_lru when faulting the object, to ensure the > pages are visible to the shrinker, if needed. > - Add back the adjust_lru when in i915_ttm_move (Thomas) > v6(Reported-by: kernel test robot <lkp@xxxxxxxxx>): > - Remove unused i915_tt > > Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx> > Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx> > Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx> #v4 R-B also for v6. Note that this may clash with a recent patch by Jason Gunthorpe that removes the last argument of ttm_bo_vm_fault_reserved(). /Thomas > --- > drivers/gpu/drm/i915/gem/i915_gem_object.h | 8 ++ > .../gpu/drm/i915/gem/i915_gem_object_types.h | 14 ++- > drivers/gpu/drm/i915/gem/i915_gem_pages.c | 5 +- > drivers/gpu/drm/i915/gem/i915_gem_shrinker.c | 45 ++++++++-- > drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 87 ++++++++++++++++- > -- > 5 files changed, 137 insertions(+), 22 deletions(-) > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h > b/drivers/gpu/drm/i915/gem/i915_gem_object.h > index e641db297e0e..3eac8cf2ae10 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h > +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h > @@ -294,6 +294,12 @@ i915_gem_object_is_shrinkable(const struct > drm_i915_gem_object *obj) > return i915_gem_object_type_has(obj, > I915_GEM_OBJECT_IS_SHRINKABLE); > } > > +static inline bool > +i915_gem_object_has_self_managed_shrink_list(const struct > drm_i915_gem_object *obj) > +{ > + return i915_gem_object_type_has(obj, > I915_GEM_OBJECT_SELF_MANAGED_SHRINK_LIST); > +} > + > static inline bool > i915_gem_object_is_proxy(const struct drm_i915_gem_object *obj) > { > @@ -531,6 +537,8 @@ i915_gem_object_pin_to_display_plane(struct > drm_i915_gem_object *obj, > > void i915_gem_object_make_unshrinkable(struct drm_i915_gem_object > *obj); > void i915_gem_object_make_shrinkable(struct drm_i915_gem_object > *obj); > +void __i915_gem_object_make_shrinkable(struct drm_i915_gem_object > *obj); > +void __i915_gem_object_make_purgeable(struct drm_i915_gem_object > *obj); > void i915_gem_object_make_purgeable(struct drm_i915_gem_object > *obj); > > static inline bool cpu_write_needs_clflush(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 f4233c4e8d2e..5718a09f5533 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h > +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h > @@ -34,9 +34,11 @@ struct i915_lut_handle { > > struct drm_i915_gem_object_ops { > unsigned int flags; > -#define I915_GEM_OBJECT_IS_SHRINKABLE BIT(1) > -#define I915_GEM_OBJECT_IS_PROXY BIT(2) > -#define I915_GEM_OBJECT_NO_MMAP BIT(3) > +#define I915_GEM_OBJECT_IS_SHRINKABLE BIT(1) > +/* Skip the shrinker management in set_pages/unset_pages */ > +#define I915_GEM_OBJECT_SELF_MANAGED_SHRINK_LIST BIT(2) > +#define I915_GEM_OBJECT_IS_PROXY BIT(3) > +#define > I915_GEM_OBJECT_NO_MMAP BIT(4) > > /* Interface between the GEM object and its backing storage. > * get_pages() is called once prior to the use of the > associated set > @@ -485,6 +487,12 @@ struct drm_i915_gem_object { > */ > atomic_t shrink_pin; > > + /** > + * @ttm_shrinkable: True when the object is using > shmem pages > + * underneath. Protected by the object lock. > + */ > + bool ttm_shrinkable; > + > /** > * Priority list of potential placements for this > object. > */ > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c > b/drivers/gpu/drm/i915/gem/i915_gem_pages.c > index ea6d9b3d2d6b..308e22a80af4 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c > +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c > @@ -68,7 +68,7 @@ void __i915_gem_object_set_pages(struct > drm_i915_gem_object *obj, > shrinkable = false; > } > > - if (shrinkable) { > + if (shrinkable && > !i915_gem_object_has_self_managed_shrink_list(obj)) { > struct list_head *list; > unsigned long flags; > > @@ -210,7 +210,8 @@ __i915_gem_object_unset_pages(struct > drm_i915_gem_object *obj) > if (i915_gem_object_is_volatile(obj)) > obj->mm.madv = I915_MADV_WILLNEED; > > - i915_gem_object_make_unshrinkable(obj); > + if (!i915_gem_object_has_self_managed_shrink_list(obj)) > + i915_gem_object_make_unshrinkable(obj); > > if (obj->mm.mapping) { > unmap_object(obj, page_mask_bits(obj->mm.mapping)); > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c > b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c > index 66121fedc655..dde0a5c232f8 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c > +++ b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c > @@ -497,13 +497,12 @@ void i915_gem_object_make_unshrinkable(struct > drm_i915_gem_object *obj) > spin_unlock_irqrestore(&i915->mm.obj_lock, flags); > } > > -static void __i915_gem_object_make_shrinkable(struct > drm_i915_gem_object *obj, > - struct list_head *head) > +static void ___i915_gem_object_make_shrinkable(struct > drm_i915_gem_object *obj, > + struct list_head > *head) > { > struct drm_i915_private *i915 = obj_to_i915(obj); > unsigned long flags; > > - GEM_BUG_ON(!i915_gem_object_has_pages(obj)); > if (!i915_gem_object_is_shrinkable(obj)) > return; > > @@ -523,6 +522,38 @@ static void > __i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj, > spin_unlock_irqrestore(&i915->mm.obj_lock, flags); > } > > +/** > + * __i915_gem_object_make_shrinkable - Move the object to the tail > of the > + * shrinkable list. Objects on this list might be swapped out. Used > with > + * WILLNEED objects. > + * @obj: The GEM object. > + * > + * DO NOT USE. This is intended to be called on very special objects > that don't > + * yet have mm.pages, but are guaranteed to have potentially > reclaimable pages > + * underneath. > + */ > +void __i915_gem_object_make_shrinkable(struct drm_i915_gem_object > *obj) > +{ > + ___i915_gem_object_make_shrinkable(obj, > + &obj_to_i915(obj)- > >mm.shrink_list); > +} > + > +/** > + * __i915_gem_object_make_purgeable - Move the object to the tail of > the > + * purgeable list. Objects on this list might be swapped out. Used > with > + * DONTNEED objects. > + * @obj: The GEM object. > + * > + * DO NOT USE. This is intended to be called on very special objects > that don't > + * yet have mm.pages, but are guaranteed to have potentially > reclaimable pages > + * underneath. > + */ > +void __i915_gem_object_make_purgeable(struct drm_i915_gem_object > *obj) > +{ > + ___i915_gem_object_make_shrinkable(obj, > + &obj_to_i915(obj)- > >mm.purge_list); > +} > + > /** > * i915_gem_object_make_shrinkable - Move the object to the tail of > the > * shrinkable list. Objects on this list might be swapped out. Used > with > @@ -535,8 +566,8 @@ static void > __i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj, > */ > void i915_gem_object_make_shrinkable(struct drm_i915_gem_object > *obj) > { > - __i915_gem_object_make_shrinkable(obj, > - &obj_to_i915(obj)- > >mm.shrink_list); > + GEM_BUG_ON(!i915_gem_object_has_pages(obj)); > + __i915_gem_object_make_shrinkable(obj); > } > > /** > @@ -552,6 +583,6 @@ void i915_gem_object_make_shrinkable(struct > drm_i915_gem_object *obj) > */ > void i915_gem_object_make_purgeable(struct drm_i915_gem_object *obj) > { > - __i915_gem_object_make_shrinkable(obj, > - &obj_to_i915(obj)- > >mm.purge_list); > + GEM_BUG_ON(!i915_gem_object_has_pages(obj)); > + __i915_gem_object_make_purgeable(obj); > } > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c > b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c > index 0fe1eb8f38e9..8de1031a2c6e 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c > +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c > @@ -762,6 +762,7 @@ static int i915_ttm_move(struct ttm_buffer_object > *bo, bool evict, > obj->ttm.get_io_page.sg_idx = 0; > } > > + i915_ttm_adjust_lru(obj); > i915_ttm_adjust_gem_after_move(obj); > return 0; > } > @@ -851,7 +852,6 @@ static int __i915_ttm_get_pages(struct > drm_i915_gem_object *obj, > return i915_ttm_err_to_gem(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) > @@ -862,19 +862,15 @@ static int __i915_ttm_get_pages(struct > drm_i915_gem_object *obj, > } > > if (!i915_gem_object_has_pages(obj)) { > - struct i915_ttm_tt *i915_tt = > - container_of(bo->ttm, typeof(*i915_tt), ttm); > - > /* 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)); > - if (!bo->ttm || !i915_tt->is_shmem) > - i915_gem_object_make_unshrinkable(obj); > } > > + i915_ttm_adjust_lru(obj); > return ret; > } > > @@ -945,8 +941,6 @@ static void i915_ttm_put_pages(struct > drm_i915_gem_object *obj, > * If the object is not destroyed next, The TTM eviction > logic > * and shrinkers will move it out if needed. > */ > - > - i915_ttm_adjust_lru(obj); > } > > static void i915_ttm_adjust_lru(struct drm_i915_gem_object *obj) > @@ -954,6 +948,8 @@ static void i915_ttm_adjust_lru(struct > drm_i915_gem_object *obj) > struct ttm_buffer_object *bo = i915_gem_to_ttm(obj); > struct i915_ttm_tt *i915_tt = > container_of(bo->ttm, typeof(*i915_tt), ttm); > + bool shrinkable = > + bo->ttm && i915_tt->filp && ttm_tt_is_populated(bo- > >ttm); > > /* > * Don't manipulate the TTM LRUs while in TTM bo destruction. > @@ -962,11 +958,40 @@ static void i915_ttm_adjust_lru(struct > drm_i915_gem_object *obj) > if (!kref_read(&bo->kref)) > return; > > + /* > + * We skip managing the shrinker LRU in set_pages() and just > manage > + * everything here. This does at least solve the issue with > having > + * temporary shmem mappings(like with evicted lmem) not being > visible to > + * the shrinker. Only our shmem objects are shrinkable, > everything else > + * we keep as unshrinkable. > + * > + * To make sure everything plays nice we keep an extra shrink > pin in TTM > + * if the underlying pages are not currently shrinkable. Once > we release > + * our pin, like when the pages are moved to shmem, the pages > will then > + * be added to the shrinker LRU, assuming the caller isn't > also holding > + * a pin. > + * > + * TODO: consider maybe also bumping the shrinker list here > when we have > + * already unpinned it, which should give us something more > like an LRU. > + */ > + if (shrinkable != obj->mm.ttm_shrinkable) { > + if (shrinkable) { > + if (obj->mm.madv == I915_MADV_WILLNEED) > + __i915_gem_object_make_shrinkable(obj > ); > + else > + __i915_gem_object_make_purgeable(obj) > ; > + } else { > + i915_gem_object_make_unshrinkable(obj); > + } > + > + obj->mm.ttm_shrinkable = shrinkable; > + } > + > /* > * Put on the correct LRU list depending on the MADV status > */ > spin_lock(&bo->bdev->lru_lock); > - if (bo->ttm && i915_tt->filp) { > + if (shrinkable) { > /* Try to keep shmem_tt from being considered for > shrinking. */ > bo->priority = TTM_MAX_BO_PRIORITY - 1; > } else if (obj->mm.madv != I915_MADV_WILLNEED) { > @@ -1010,13 +1035,34 @@ static vm_fault_t vm_fault_ttm(struct > vm_fault *vmf) > struct vm_area_struct *area = vmf->vma; > struct drm_i915_gem_object *obj = > i915_ttm_to_gem(area->vm_private_data); > + struct ttm_buffer_object *bo = i915_gem_to_ttm(obj); > + struct drm_device *dev = bo->base.dev; > + vm_fault_t ret; > + int idx; > > /* Sanity check that we allow writing into this object */ > if (unlikely(i915_gem_object_is_readonly(obj) && > area->vm_flags & VM_WRITE)) > return VM_FAULT_SIGBUS; > > - return ttm_bo_vm_fault(vmf); > + ret = ttm_bo_vm_reserve(bo, vmf); > + if (ret) > + return ret; > + > + if (drm_dev_enter(dev, &idx)) { > + ret = ttm_bo_vm_fault_reserved(vmf, vmf->vma- > >vm_page_prot, > + > TTM_BO_VM_NUM_PREFAULT, 1); > + drm_dev_exit(idx); > + } else { > + ret = ttm_bo_vm_dummy_page(vmf, vmf->vma- > >vm_page_prot); > + } > + if (ret == VM_FAULT_RETRY && !(vmf->flags & > FAULT_FLAG_RETRY_NOWAIT)) > + return ret; > + > + i915_ttm_adjust_lru(obj); > + > + dma_resv_unlock(bo->base.resv); > + return ret; > } > > static int > @@ -1067,6 +1113,7 @@ static u64 i915_ttm_mmap_offset(struct > drm_i915_gem_object *obj) > > static const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = { > .name = "i915_gem_object_ttm", > + .flags = I915_GEM_OBJECT_SELF_MANAGED_SHRINK_LIST, > > .get_pages = i915_ttm_get_pages, > .put_pages = i915_ttm_put_pages, > @@ -1089,6 +1136,18 @@ void i915_ttm_bo_destroy(struct > ttm_buffer_object *bo) > mutex_destroy(&obj->ttm.get_io_page.lock); > > if (obj->ttm.created) { > + /* > + * We freely manage the shrinker LRU outide of the > mm.pages life > + * cycle. As a result when destroying the object we > should be > + * extra paranoid and ensure we remove it from the > LRU, before > + * we free the object. > + * > + * Touching the ttm_shrinkable outside of the object > lock here > + * should be safe now that the last GEM object ref > was dropped. > + */ > + if (obj->mm.ttm_shrinkable) > + i915_gem_object_make_unshrinkable(obj); > + > i915_ttm_backup_free(obj); > > /* This releases all gem object bindings to the > backend. */ > @@ -1141,6 +1200,14 @@ int __i915_gem_ttm_object_init(struct > intel_memory_region *mem, > /* Forcing the page size is kernel internal only */ > GEM_BUG_ON(page_size && obj->mm.n_placements); > > + /* > + * Keep an extra shrink pin to prevent the object from being > made > + * shrinkable too early. If the ttm_tt is ever allocated in > shmem, we > + * drop the pin. The TTM backend manages the shrinker LRU > itself, > + * outside of the normal mm.pages life cycle. > + */ > + i915_gem_object_make_unshrinkable(obj); > + > /* > * If this function fails, it will call the destructor, but > * our caller still owns the object. So no freeing in the