Re: [PATCH v8 2/5] drm: ttm_pool: Rework ttm_pool to use drm_page_pool

Am 05.03.21 um 00:20 schrieb John Stultz:

This patch reworks the ttm_pool logic to utilize the recently added drm_page_pool code.

This adds drm_page_pool structures to the ttm_pool_type structures, and then removes all the ttm_pool_type shrinker logic (as its handled in the drm_page_pool shrinker).

NOTE: There is one mismatch in the interfaces I'm not totally happy with. The ttm_pool tracks all of its pooled pages across a number of different pools, and tries to keep this size under the specified page_pool_size value. With the drm_page_pool, there may other users, however there is still one global shrinker list of pools. So we can't easily reduce the ttm pool under the ttm specified size without potentially doing a lot of shrinking to other non-ttm pools. So either we can:

1. Try to split it so each user of drm_page_pools manages its own pool shrinking.
2. Push the max value into the drm_page_pool, and have it manage shrinking to fit under that global max. Then share those size/max values out so the ttm_pool debug output can have more context.

I've taken the second path in this patch set, but wanted to call it out so folks could look closely.

That's perfectly fine with me. A global approach for the different page pool types is desired anyway as far as I can see.

Thoughts would be greatly appreciated here!

Cc: Daniel Vetter daniel@ffwll.ch Cc: Christian Koenig christian.koenig@amd.com Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Liam Mark lmark@codeaurora.org Cc: Chris Goldsworthy cgoldswo@codeaurora.org Cc: Laura Abbott labbott@kernel.org Cc: Brian Starkey Brian.Starkey@arm.com Cc: Hridya Valsaraju hridya@google.com Cc: Suren Baghdasaryan surenb@google.com Cc: Sandeep Patil sspatil@google.com Cc: Daniel Mentz danielmentz@google.com Cc: Ørjan Eide orjan.eide@arm.com Cc: Robin Murphy robin.murphy@arm.com Cc: Ezequiel Garcia ezequiel@collabora.com Cc: Simon Ser contact@emersion.fr Cc: James Jones jajones@nvidia.com Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Signed-off-by: John Stultz john.stultz@linaro.org

---

v7:

• Major refactoring to use drm_page_pools inside the ttm_pool_type structure. This allows us to use container_of to get the needed context to free a page. This also means less code is changed overall.

v8:

• Reworked to use the new cleanly rewritten drm_page_pool logic

---

drivers/gpu/drm/Kconfig | 1 + drivers/gpu/drm/ttm/ttm_pool.c | 156 ++++++--------------------------- include/drm/ttm/ttm_pool.h | 6 +- 3 files changed, 31 insertions(+), 132 deletions(-)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig index 7cbcecb8f7df..a6cbdb63f6c7 100644 --- a/drivers/gpu/drm/Kconfig +++ b/drivers/gpu/drm/Kconfig @@ -184,6 +184,7 @@ config DRM_PAGE_POOL config DRM_TTM tristate depends on DRM && MMU

• select DRM_PAGE_POOL help GPU memory management subsystem for devices with multiple GPU memory types. Will be enabled automatically if a device driver

diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c index 6e27cb1bf48b..f74ea801d7ab 100644 --- a/drivers/gpu/drm/ttm/ttm_pool.c +++ b/drivers/gpu/drm/ttm/ttm_pool.c @@ -39,6 +39,7 @@ #include <asm/set_memory.h> #endif

+#include <drm/page_pool.h> #include <drm/ttm/ttm_pool.h> #include <drm/ttm/ttm_bo_driver.h> #include <drm/ttm/ttm_tt.h> @@ -68,8 +69,6 @@ static struct ttm_pool_type global_dma32_write_combined[MAX_ORDER]; static struct ttm_pool_type global_dma32_uncached[MAX_ORDER];

static struct mutex shrinker_lock; -static struct list_head shrinker_list; -static struct shrinker mm_shrinker;

/* Allocate pages of size 1 << order with the given gfp_flags */ static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t gfp_flags, @@ -125,8 +124,9 @@ static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t gfp_flags, }

/* Reset the caching and pages of size 1 << order */ -static void ttm_pool_free_page(struct ttm_pool *pool, enum ttm_caching caching,

• 	       unsigned int order, struct page *p)
  

+static unsigned long ttm_pool_free_page(struct ttm_pool *pool,

• 			enum ttm_caching caching,
  

• 			unsigned int order, struct page *p)
  

  { unsigned long attr = DMA_ATTR_FORCE_CONTIGUOUS; struct ttm_pool_dma *dma;

@@ -142,7 +142,7 @@ static void ttm_pool_free_page(struct ttm_pool *pool, enum ttm_caching caching,

if (!pool || !pool->use_dma_alloc) { __free_pages(p, order);

• return;
  

• return 1UL << order;
  

  }

  if (order)

@@ -153,6 +153,16 @@ static void ttm_pool_free_page(struct ttm_pool *pool, enum ttm_caching caching, dma_free_attrs(pool->dev, (1UL << order) * PAGE_SIZE, vaddr, dma->addr, attr); kfree(dma);

• return 1UL << order;

The returned value is always the same. So you wrapper can do this and we don't really need to change the function here.

+}

+static unsigned long ttm_subpool_free_page(struct drm_page_pool *subpool,

• 			   struct page *p)
  

Better call this ttm_pool_free_callback.

+{

• struct ttm_pool_type *pt;

• pt = container_of(subpool, struct ttm_pool_type, subpool);

• return ttm_pool_free_page(pt->pool, pt->caching, pt->order, p); }

  /* Apply a new caching to an array of pages */

@@ -216,40 +226,6 @@ static void ttm_pool_unmap(struct ttm_pool *pool, dma_addr_t dma_addr, DMA_BIDIRECTIONAL); }

-/* Give pages into a specific pool_type */ -static void ttm_pool_type_give(struct ttm_pool_type *pt, struct page *p) -{

• unsigned int i, num_pages = 1 << pt->order;
• for (i = 0; i < num_pages; ++i) {

• if (PageHighMem(p))
  

• 	clear_highpage(p + i);
  

• else
  

• 	clear_page(page_address(p + i));
  

• }
• spin_lock(&pt->lock);
• list_add(&p->lru, &pt->pages);
• spin_unlock(&pt->lock);
• atomic_long_add(1 << pt->order, &allocated_pages);

-}

-/* Take pages from a specific pool_type, return NULL when nothing available */ -static struct page *ttm_pool_type_take(struct ttm_pool_type *pt) -{

• struct page *p;
• spin_lock(&pt->lock);
• p = list_first_entry_or_null(&pt->pages, typeof(*p), lru);
• if (p) {

• atomic_long_sub(1 << pt->order, &allocated_pages);
  

• list_del(&p->lru);
  

• }
• spin_unlock(&pt->lock);
• return p;

-}

• /* Initialize and add a pool type to the global shrinker list */ static void ttm_pool_type_init(struct ttm_pool_type *pt, struct ttm_pool *pool, enum ttm_caching caching, unsigned int order)

@@ -257,25 +233,14 @@ static void ttm_pool_type_init(struct ttm_pool_type *pt, struct ttm_pool *pool, pt->pool = pool; pt->caching = caching; pt->order = order;

The order is now duplicated and can probably be dropped from the TTM pool.

• spin_lock_init(&pt->lock);

• INIT_LIST_HEAD(&pt->pages);

• mutex_lock(&shrinker_lock);

• list_add_tail(&pt->shrinker_list, &shrinker_list);

• mutex_unlock(&shrinker_lock);

• drm_page_pool_init(&pt->subpool, order, ttm_subpool_free_page); }

  /* Remove a pool_type from the global shrinker list and free all pages */ static void ttm_pool_type_fini(struct ttm_pool_type *pt) {

• struct page *p, *tmp;
• mutex_lock(&shrinker_lock);
• list_del(&pt->shrinker_list);
• mutex_unlock(&shrinker_lock);
• list_for_each_entry_safe(p, tmp, &pt->pages, lru)

• ttm_pool_free_page(pt->pool, pt->caching, pt->order, p);
  

• drm_page_pool_fini(&pt->subpool); }

  /* Return the pool_type to use for the given caching and order */

@@ -306,30 +271,6 @@ static struct ttm_pool_type *ttm_pool_select_type(struct ttm_pool *pool, return NULL; }

-/* Free pages using the global shrinker list */ -static unsigned int ttm_pool_shrink(void) -{

• struct ttm_pool_type *pt;
• unsigned int num_freed;
• struct page *p;
• mutex_lock(&shrinker_lock);
• pt = list_first_entry(&shrinker_list, typeof(*pt), shrinker_list);
• p = ttm_pool_type_take(pt);
• if (p) {

• ttm_pool_free_page(pt->pool, pt->caching, pt->order, p);
  

• num_freed = 1 << pt->order;
  

• } else {

• num_freed = 0;
  

• }
• list_move_tail(&pt->shrinker_list, &shrinker_list);
• mutex_unlock(&shrinker_lock);
• return num_freed;

-}

• /* Return the allocation order based for a page */ static unsigned int ttm_pool_page_order(struct ttm_pool *pool, struct page *p) {

@@ -386,7 +327,7 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt, struct ttm_pool_type *pt;

pt = ttm_pool_select_type(pool, tt->caching, order);

• p = pt ? ttm_pool_type_take(pt) : NULL;
  

• p = pt ? drm_page_pool_remove(&pt->subpool) : NULL;
  

  if (p) { apply_caching = true; } else {

@@ -479,16 +420,13 @@ void ttm_pool_free(struct ttm_pool *pool, struct ttm_tt *tt)

pt = ttm_pool_select_type(pool, tt->caching, order);
if (pt)

• 	ttm_pool_type_give(pt, tt->pages[i]);
  

• 	drm_page_pool_add(&pt->subpool, tt->pages[i]);
  

  else ttm_pool_free_page(pool, tt->caching, order, tt->pages[i]);

  i += num_pages; }

• while (atomic_long_read(&allocated_pages) > page_pool_size)

• ttm_pool_shrink();
  

That won't work. You still need to make sure that we shrink the pool to be under the maximum.

} EXPORT_SYMBOL(ttm_pool_free);

@@ -537,21 +475,6 @@ void ttm_pool_fini(struct ttm_pool *pool) }

#ifdef CONFIG_DEBUG_FS -/* Count the number of pages available in a pool_type */ -static unsigned int ttm_pool_type_count(struct ttm_pool_type *pt) -{

• unsigned int count = 0;
• struct page *p;
• spin_lock(&pt->lock);
• /* Only used for debugfs, the overhead doesn't matter */
• list_for_each_entry(p, &pt->pages, lru)

• ++count;
  

• spin_unlock(&pt->lock);
• return count;

-}

• /* Dump information about the different pool types */ static void ttm_pool_debugfs_orders(struct ttm_pool_type *pt, struct seq_file *m)

@@ -559,7 +482,8 @@ static void ttm_pool_debugfs_orders(struct ttm_pool_type *pt, unsigned int i;

for (i = 0; i < MAX_ORDER; ++i)

• seq_printf(m, " %8u", ttm_pool_type_count(&pt[i]));
  

• seq_printf(m, " %8lu",
  

• 	   drm_page_pool_get_size(&pt[i].subpool));
  

  seq_puts(m, "\n"); }

@@ -609,7 +533,10 @@ int ttm_pool_debugfs(struct ttm_pool *pool, struct seq_file *m) }

seq_printf(m, "\ntotal\t: %8lu of %8lu\n",

•    atomic_long_read(&allocated_pages), page_pool_size);
  

•    atomic_long_read(&allocated_pages),
  

•    drm_page_pool_get_max());
  

• seq_printf(m, "(%8lu in non-ttm pools)\n", drm_page_pool_get_total() -

• 			atomic_long_read(&allocated_pages));
  
  

  mutex_unlock(&shrinker_lock);

That won't work. You need to move the debugfs functions into the DRM pool as well or otherwise you have two separate shrinker_lock instances and the lock protection is not correct any more.

Regards, Christian.

@@ -619,28 +546,6 @@ EXPORT_SYMBOL(ttm_pool_debugfs);

#endif

-/* As long as pages are available make sure to release at least one */ -static unsigned long ttm_pool_shrinker_scan(struct shrinker *shrink,

• 			    struct shrink_control *sc)
  

-{

• unsigned long num_freed = 0;
• do

• num_freed += ttm_pool_shrink();
  

• while (!num_freed && atomic_long_read(&allocated_pages));
• return num_freed;

-}

-/* Return the number of pages available or SHRINK_EMPTY if we have none */ -static unsigned long ttm_pool_shrinker_count(struct shrinker *shrink,

• 			     struct shrink_control *sc)
  

-{

• unsigned long num_pages = atomic_long_read(&allocated_pages);
• return num_pages ? num_pages : SHRINK_EMPTY;

-}

• /**
  • ttm_pool_mgr_init - Initialize globals

@@ -655,8 +560,9 @@ int ttm_pool_mgr_init(unsigned long num_pages) if (!page_pool_size) page_pool_size = num_pages;

• drm_page_pool_set_max(page_pool_size);
• mutex_init(&shrinker_lock);

• INIT_LIST_HEAD(&shrinker_list);

  for (i = 0; i < MAX_ORDER; ++i) { ttm_pool_type_init(&global_write_combined[i], NULL,

@@ -669,10 +575,7 @@ int ttm_pool_mgr_init(unsigned long num_pages) ttm_uncached, i); }

• mm_shrinker.count_objects = ttm_pool_shrinker_count;
• mm_shrinker.scan_objects = ttm_pool_shrinker_scan;
• mm_shrinker.seeks = 1;
• return register_shrinker(&mm_shrinker);

• return 0; }

  /**

@@ -691,7 +594,4 @@ void ttm_pool_mgr_fini(void) ttm_pool_type_fini(&global_dma32_write_combined[i]); ttm_pool_type_fini(&global_dma32_uncached[i]); }

• unregister_shrinker(&mm_shrinker);
• WARN_ON(!list_empty(&shrinker_list)); }

diff --git a/include/drm/ttm/ttm_pool.h b/include/drm/ttm/ttm_pool.h index 4321728bdd11..3d975888ce47 100644 --- a/include/drm/ttm/ttm_pool.h +++ b/include/drm/ttm/ttm_pool.h @@ -30,6 +30,7 @@ #include <linux/llist.h> #include <linux/spinlock.h> #include <drm/ttm/ttm_caching.h> +#include <drm/page_pool.h>

struct device; struct ttm_tt; @@ -51,10 +52,7 @@ struct ttm_pool_type { unsigned int order; enum ttm_caching caching;

• struct list_head shrinker_list;
• spinlock_t lock;
• struct list_head pages;

• struct drm_page_pool subpool; };

  /**