[PATCH 2/2] driver: dma-buf: use alloc_pages_bulk_list for order-0 allocation

["zhaoyang.huang" <zhaoyang.huang@unisoc.com>]

From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>

The size of once dma-buf allocation could be dozens MB or much more
which introduce a loop of allocating several thousands of order-0 pages.
Furthermore, the concurrent allocation could have dma-buf allocation enter
direct-reclaim during the loop. This commit would like to eliminate the
above two affections by introducing alloc_pages_bulk_list in dma-buf's
order-0 allocation. This patch is proved to be conditionally helpful
in 18MB allocation as decreasing the time from 24604us to 6555us and no
harm when bulk allocation can't be done(fallback to single page
allocation)

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
 drivers/dma-buf/heaps/system_heap.c | 36 +++++++++++++++++++----------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index bbe7881f1360..71b028c63bd8 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -300,8 +300,8 @@ static const struct dma_buf_ops system_heap_buf_ops = {
 	.release = system_heap_dma_buf_release,
 };
 
-static struct page *alloc_largest_available(unsigned long size,
-					    unsigned int max_order)
+static void alloc_largest_available(unsigned long size,
+		    unsigned int max_order, unsigned int *num_pages, struct list_head *list)
 {
 	struct page *page;
 	int i;
@@ -312,12 +312,19 @@ static struct page *alloc_largest_available(unsigned long size,
 		if (max_order < orders[i])
 			continue;
 
-		page = alloc_pages(order_flags[i], orders[i]);
-		if (!page)
+		if (orders[i]) {
+			page = alloc_pages(order_flags[i], orders[i]);
+			if (page) {
+				list_add(&page->lru, list);
+				*num_pages = 1;
+			}
+		} else
+			*num_pages = alloc_pages_bulk_list(LOW_ORDER_GFP, size / PAGE_SIZE, list);
+
+		if (list_empty(list))
 			continue;
-		return page;
+		return;
 	}
-	return NULL;
 }
 
 static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
@@ -335,6 +342,8 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
 	struct list_head pages;
 	struct page *page, *tmp_page;
 	int i, ret = -ENOMEM;
+	unsigned int num_pages;
+	LIST_HEAD(head);
 
 	buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
 	if (!buffer)
@@ -348,6 +357,8 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
 	INIT_LIST_HEAD(&pages);
 	i = 0;
 	while (size_remaining > 0) {
+		num_pages = 0;
+		INIT_LIST_HEAD(&head);
 		/*
 		 * Avoid trying to allocate memory if the process
 		 * has been killed by SIGKILL
@@ -357,14 +368,15 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
 			goto free_buffer;
 		}
 
-		page = alloc_largest_available(size_remaining, max_order);
-		if (!page)
+		alloc_largest_available(size_remaining, max_order, &num_pages, &head);
+		if (!num_pages)
 			goto free_buffer;
 
-		list_add_tail(&page->lru, &pages);
-		size_remaining -= page_size(page);
-		max_order = compound_order(page);
-		i++;
+		list_splice_tail(&head, &pages);
+		max_order = folio_order(lru_to_folio(&head));
+		size_remaining -= PAGE_SIZE * (num_pages << max_order);
+		i += num_pages;
+
 	}
 
 	table = &buffer->sg_table;
-- 
2.25.1