[RFC][PATCH v6 7/7] dma-buf: system_heap: Add deferred freeing to the system heap

[John Stultz <john.stultz@xxxxxxxxxx>]

Utilize the deferred free helper library in the system heap.

This provides a nice performance bump and puts the
system heap performance on par with ION.

Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Christian Koenig <christian.koenig@xxxxxxx>
Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Cc: Liam Mark <lmark@xxxxxxxxxxxxxx>
Cc: Chris Goldsworthy <cgoldswo@xxxxxxxxxxxxxx>
Cc: Laura Abbott <labbott@xxxxxxxxxx>
Cc: Brian Starkey <Brian.Starkey@xxxxxxx>
Cc: Hridya Valsaraju <hridya@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Sandeep Patil <sspatil@xxxxxxxxxx>
Cc: Daniel Mentz <danielmentz@xxxxxxxxxx>
Cc: Ørjan Eide <orjan.eide@xxxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Cc: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx>
Cc: Simon Ser <contact@xxxxxxxxxxx>
Cc: James Jones <jajones@xxxxxxxxxx>
Cc: linux-media@xxxxxxxxxxxxxxx
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
v2:
* Rework deferred-free api to use reason enum as suggested by
  Suren Baghdasaryan
---
 drivers/dma-buf/heaps/Kconfig       |  1 +
 drivers/dma-buf/heaps/system_heap.c | 31 ++++++++++++++++++++++-------
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
index 7e28934e0def..10632ccfb4a5 100644
--- a/drivers/dma-buf/heaps/Kconfig
+++ b/drivers/dma-buf/heaps/Kconfig
@@ -5,6 +5,7 @@ config DMABUF_HEAPS_SYSTEM
 	bool "DMA-BUF System Heap"
 	depends on DMABUF_HEAPS
 	select DRM_PAGE_POOL
+	select DMABUF_HEAPS_DEFERRED_FREE
 	help
 	  Choose this option to enable the system dmabuf heap. The system heap
 	  is backed by pages from the buddy allocator. If in doubt, say Y.
diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index 6d39e9f32e36..042244407db5 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -22,6 +22,7 @@
 #include <linux/vmalloc.h>
 
 #include <drm/page_pool.h>
+#include "deferred-free-helper.h"
 
 static struct dma_heap *sys_heap;
 
@@ -33,6 +34,7 @@ struct system_heap_buffer {
 	struct sg_table sg_table;
 	int vmap_cnt;
 	void *vaddr;
+	struct deferred_freelist_item deferred_free;
 };
 
 struct dma_heap_attachment {
@@ -308,30 +310,45 @@ static int system_heap_zero_buffer(struct system_heap_buffer *buffer)
 	return ret;
 }
 
-static void system_heap_dma_buf_release(struct dma_buf *dmabuf)
+static void system_heap_buf_free(struct deferred_freelist_item *item,
+				 enum df_reason reason)
 {
-	struct system_heap_buffer *buffer = dmabuf->priv;
+	struct system_heap_buffer *buffer;
 	struct sg_table *table;
 	struct scatterlist *sg;
 	int i, j;
 
+	buffer = container_of(item, struct system_heap_buffer, deferred_free);
 	/* Zero the buffer pages before adding back to the pool */
-	system_heap_zero_buffer(buffer);
+	if (reason == DF_NORMAL)
+		if (system_heap_zero_buffer(buffer))
+			reason = DF_UNDER_PRESSURE; // On failure, just free
 
 	table = &buffer->sg_table;
 	for_each_sg(table->sgl, sg, table->nents, i) {
 		struct page *page = sg_page(sg);
 
-		for (j = 0; j < NUM_ORDERS; j++) {
-			if (compound_order(page) == orders[j])
-				break;
+		if (reason == DF_UNDER_PRESSURE) {
+			__free_pages(page, compound_order(page));
+		} else {
+			for (j = 0; j < NUM_ORDERS; j++) {
+				if (compound_order(page) == orders[j])
+					break;
+			}
+			drm_page_pool_add(pools[j], page);
 		}
-		drm_page_pool_add(pools[j], page);
 	}
 	sg_free_table(table);
 	kfree(buffer);
 }
 
+static void system_heap_dma_buf_release(struct dma_buf *dmabuf)
+{
+	struct system_heap_buffer *buffer = dmabuf->priv;
+
+	deferred_free(&buffer->deferred_free, system_heap_buf_free, buffer->len);
+}
+
 static const struct dma_buf_ops system_heap_buf_ops = {
 	.attach = system_heap_attach,
 	.detach = system_heap_detach,
-- 
2.25.1