[RFC PATCH v2 13/13] drm/i915: Use the TTM shrinker rather than the external shmem pool.
Thomas Hellström
thomas.hellstrom at linux.intel.com
Thu Feb 9 18:26:32 UTC 2023
Remove the external i915 TTM shmem pool and replace it with the
normal TTM page allocation. Also provide a callback for the TTM
shrinker functionality.
Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
---
.../gpu/drm/i915/gem/i915_gem_object_types.h | 6 -
drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 265 ++++--------------
2 files changed, 47 insertions(+), 224 deletions(-)
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 19c9bdd8f905..511dc1384a9c 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
@@ -544,12 +544,6 @@ 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;
-
/**
* @unknown_state: Indicate that the object is effectively
* borked. This is write-once and set if we somehow encounter a
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index 341b94672abc..c9281db73255 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -3,8 +3,6 @@
* Copyright © 2021 Intel Corporation
*/
-#include <linux/shmem_fs.h>
-
#include <drm/ttm/ttm_placement.h>
#include <drm/ttm/ttm_tt.h>
#include <drm/drm_buddy.h>
@@ -37,8 +35,6 @@
* @ttm: The base TTM page vector.
* @dev: The struct device used for dma mapping and unmapping.
* @cached_rsgt: The cached scatter-gather table.
- * @is_shmem: Set if using shmem.
- * @filp: The shmem file, if using shmem backend.
*
* Note that DMA may be going on right up to the point where the page-
* vector is unpopulated in delayed destroy. Hence keep the
@@ -50,9 +46,6 @@ struct i915_ttm_tt {
struct ttm_tt ttm;
struct device *dev;
struct i915_refct_sgt cached_rsgt;
-
- bool is_shmem;
- struct file *filp;
};
static const struct ttm_place sys_placement_flags = {
@@ -185,75 +178,6 @@ i915_ttm_placement_from_obj(const struct drm_i915_gem_object *obj,
placement->busy_placement = busy;
}
-static int i915_ttm_tt_shmem_populate(struct ttm_device *bdev,
- struct ttm_tt *ttm,
- struct ttm_operation_ctx *ctx)
-{
- struct drm_i915_private *i915 = container_of(bdev, typeof(*i915), bdev);
- struct intel_memory_region *mr = i915->mm.regions[INTEL_MEMORY_SYSTEM];
- struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
- const unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
- const size_t size = (size_t)ttm->num_pages << PAGE_SHIFT;
- struct file *filp = i915_tt->filp;
- struct sgt_iter sgt_iter;
- struct sg_table *st;
- struct page *page;
- unsigned long i;
- int err;
-
- if (!filp) {
- struct address_space *mapping;
- gfp_t mask;
-
- filp = shmem_file_setup("i915-shmem-tt", size, VM_NORESERVE);
- if (IS_ERR(filp))
- return PTR_ERR(filp);
-
- mask = GFP_HIGHUSER | __GFP_RECLAIMABLE;
-
- mapping = filp->f_mapping;
- mapping_set_gfp_mask(mapping, mask);
- GEM_BUG_ON(!(mapping_gfp_mask(mapping) & __GFP_RECLAIM));
-
- i915_tt->filp = filp;
- }
-
- st = &i915_tt->cached_rsgt.table;
- err = shmem_sg_alloc_table(i915, st, size, mr, filp->f_mapping,
- max_segment);
- if (err)
- return err;
-
- err = dma_map_sgtable(i915_tt->dev, st, DMA_BIDIRECTIONAL,
- DMA_ATTR_SKIP_CPU_SYNC);
- if (err)
- goto err_free_st;
-
- i = 0;
- for_each_sgt_page(page, sgt_iter, st)
- ttm->pages[i++] = page;
-
- if (ttm->page_flags & TTM_TT_FLAG_SWAPPED)
- ttm->page_flags &= ~TTM_TT_FLAG_SWAPPED;
-
- return 0;
-
-err_free_st:
- shmem_sg_free_table(st, filp->f_mapping, false, false);
-
- return err;
-}
-
-static void i915_ttm_tt_shmem_unpopulate(struct ttm_tt *ttm)
-{
- struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
- bool backup = ttm->page_flags & TTM_TT_FLAG_SWAPPED;
- struct sg_table *st = &i915_tt->cached_rsgt.table;
-
- shmem_sg_free_table(st, file_inode(i915_tt->filp)->i_mapping,
- backup, backup);
-}
-
static void i915_ttm_tt_release(struct kref *ref)
{
struct i915_ttm_tt *i915_tt =
@@ -292,11 +216,6 @@ static struct ttm_tt *i915_ttm_tt_create(struct ttm_buffer_object *bo,
page_flags |= TTM_TT_FLAG_ZERO_ALLOC;
caching = i915_ttm_select_tt_caching(obj);
- if (i915_gem_object_is_shrinkable(obj) && caching == ttm_cached) {
- page_flags |= TTM_TT_FLAG_EXTERNAL |
- TTM_TT_FLAG_EXTERNAL_MAPPABLE;
- i915_tt->is_shmem = true;
- }
if (i915_gem_object_needs_ccs_pages(obj))
ccs_pages = DIV_ROUND_UP(DIV_ROUND_UP(bo->base.size,
@@ -325,9 +244,6 @@ static int i915_ttm_tt_populate(struct ttm_device *bdev,
{
struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
- if (i915_tt->is_shmem)
- return i915_ttm_tt_shmem_populate(bdev, ttm, ctx);
-
return ttm_pool_alloc(&bdev->pool, ttm, ctx);
}
@@ -339,21 +255,46 @@ static void i915_ttm_tt_unpopulate(struct ttm_device *bdev, struct ttm_tt *ttm)
if (st->sgl)
dma_unmap_sgtable(i915_tt->dev, st, DMA_BIDIRECTIONAL, 0);
- if (i915_tt->is_shmem) {
- i915_ttm_tt_shmem_unpopulate(ttm);
- } else {
- sg_free_table(st);
- ttm_pool_free(&bdev->pool, ttm);
+ sg_free_table(st);
+ ttm_pool_free(&bdev->pool, ttm);
+}
+
+static long i915_ttm_bo_shrink(struct ttm_buffer_object *bo,
+ struct ttm_operation_ctx *ctx)
+
+{
+ struct ttm_tt *tt = bo->ttm;
+ struct i915_ttm_tt *i915_tt = container_of(tt, typeof(*i915_tt), ttm);
+ struct sg_table *st = &i915_tt->cached_rsgt.table;
+ long ret;
+
+ if (!i915_ttm_is_ghost_object(bo)) {
+ struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
+ long ret = i915_ttm_move_notify(bo);
+
+ if (ret)
+ return ret;
+
+ if (obj->mm.madv == I915_MADV_DONTNEED) {
+ GEM_WARN_ON(!(tt->page_flags & TTM_TT_FLAG_DONTNEED));
+ obj->mm.madv = __I915_MADV_PURGED;
+ }
}
+
+ if (st->sgl)
+ dma_unmap_sgtable(i915_tt->dev, st, DMA_BIDIRECTIONAL, 0);
+
+ sg_free_table(st);
+
+ ret = ttm_tt_shrink(bo->bdev, tt);
+
+ return ret;
}
static void i915_ttm_tt_destroy(struct ttm_device *bdev, struct ttm_tt *ttm)
{
struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
- if (i915_tt->filp)
- fput(i915_tt->filp);
-
ttm_tt_fini(ttm);
i915_refct_sgt_put(&i915_tt->cached_rsgt);
}
@@ -439,18 +380,6 @@ int i915_ttm_purge(struct drm_i915_gem_object *obj)
if (ret)
return ret;
- if (bo->ttm && i915_tt->filp) {
- /*
- * The below fput(which eventually calls shmem_truncate) might
- * be delayed by worker, so when directly called to purge the
- * pages(like by the shrinker) we should try to be more
- * aggressive and release the pages immediately.
- */
- shmem_truncate_range(file_inode(i915_tt->filp),
- 0, (loff_t)-1);
- fput(fetch_and_zero(&i915_tt->filp));
- }
-
obj->write_domain = 0;
obj->read_domains = 0;
i915_ttm_adjust_gem_after_move(obj);
@@ -460,53 +389,6 @@ int i915_ttm_purge(struct drm_i915_gem_object *obj)
return 0;
}
-static int i915_ttm_shrink(struct drm_i915_gem_object *obj, unsigned int flags)
-{
- struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
- struct i915_ttm_tt *i915_tt =
- container_of(bo->ttm, typeof(*i915_tt), ttm);
- struct ttm_operation_ctx ctx = {
- .interruptible = true,
- .no_wait_gpu = flags & I915_GEM_OBJECT_SHRINK_NO_GPU_WAIT,
- };
- struct ttm_placement place = {};
- int ret;
-
- if (!bo->ttm || i915_ttm_cpu_maps_iomem(bo->resource))
- return 0;
-
- GEM_BUG_ON(!i915_tt->is_shmem);
-
- if (!i915_tt->filp)
- return 0;
-
- ret = ttm_bo_wait_ctx(bo, &ctx);
- if (ret)
- return ret;
-
- switch (obj->mm.madv) {
- case I915_MADV_DONTNEED:
- return i915_ttm_purge(obj);
- case __I915_MADV_PURGED:
- return 0;
- }
-
- if (bo->ttm->page_flags & TTM_TT_FLAG_SWAPPED)
- return 0;
-
- bo->ttm->page_flags |= TTM_TT_FLAG_SWAPPED;
- ret = ttm_bo_validate(bo, &place, &ctx);
- if (ret) {
- bo->ttm->page_flags &= ~TTM_TT_FLAG_SWAPPED;
- return ret;
- }
-
- if (flags & I915_GEM_OBJECT_SHRINK_WRITEBACK)
- __shmem_writeback(obj->base.size, i915_tt->filp->f_mapping);
-
- return 0;
-}
-
static void i915_ttm_delete_mem_notify(struct ttm_buffer_object *bo)
{
struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
@@ -765,6 +647,7 @@ static struct ttm_device_funcs i915_ttm_bo_driver = {
.io_mem_reserve = i915_ttm_io_mem_reserve,
.io_mem_pfn = i915_ttm_io_mem_pfn,
.access_memory = i915_ttm_access_memory,
+ .bo_shrink = i915_ttm_bo_shrink,
};
/**
@@ -931,8 +814,6 @@ 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.
@@ -941,54 +822,25 @@ 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.
- *
- * TODO: There is a small window of opportunity for this function to
- * get called from eviction after we've dropped the last GEM refcount,
- * but before the TTM deleted flag is set on the object. Avoid
- * adjusting the shrinker list in such cases, since the object is
- * not available to the shrinker anyway due to its zero refcount.
- * To fix this properly we should move to a TTM shrinker LRU list for
- * these objects.
- */
- if (kref_get_unless_zero(&obj->base.refcount)) {
- 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;
- }
- i915_gem_object_put(obj);
+ if (bo->ttm) {
+ int ret = 0;
+
+ if (obj->mm.madv == I915_MADV_DONTNEED &&
+ !ttm_tt_purgeable(bo->ttm))
+ ret = ttm_tt_set_dontneed(bo->bdev, bo->ttm);
+ else if (obj->mm.madv == I915_MADV_WILLNEED &&
+ ttm_tt_purgeable(bo->ttm))
+ ret = ttm_tt_set_willneed(bo->bdev, bo->ttm);
+
+ if (ret == -EALREADY)
+ obj->mm.madv = __I915_MADV_PURGED;
}
/*
* Put on the correct LRU list depending on the MADV status
*/
spin_lock(&bo->bdev->lru_lock);
- 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) {
+ if (obj->mm.madv != I915_MADV_WILLNEED) {
bo->priority = I915_TTM_PRIO_PURGE;
} else if (!i915_gem_object_has_pages(obj)) {
bo->priority = I915_TTM_PRIO_NO_PAGES;
@@ -1226,13 +1078,10 @@ static void i915_ttm_unmap_virtual(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_IS_SHRINKABLE |
- I915_GEM_OBJECT_SELF_MANAGED_SHRINK_LIST,
.get_pages = i915_ttm_get_pages,
.put_pages = i915_ttm_put_pages,
.truncate = i915_ttm_truncate,
- .shrink = i915_ttm_shrink,
.adjust_lru = i915_ttm_adjust_lru,
.delayed_free = i915_ttm_delayed_free,
@@ -1251,18 +1100,6 @@ 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. */
@@ -1318,14 +1155,6 @@ 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
--
2.34.1
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