Re: [RFC][PATCH 5/6] dma-buf: system_heap: Add pagepool support to system heap

From: Chris Goldsworthy
Date: Thu Oct 01 2020 - 10:49:27 EST


On 2020-09-29 21:46, Chris Goldsworthy wrote:
On 2020-09-25 21:24, John Stultz wrote:
Reuse/abuse the pagepool code from the network code to speed
up allocation performance.

This is similar to the ION pagepool usage, but tries to
utilize generic code instead of a custom implementation.

Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Cc: Liam Mark <lmark@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: 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>
---
drivers/dma-buf/heaps/Kconfig | 1 +
drivers/dma-buf/heaps/system_heap.c | 32 +++++++++++++++++++++++++----
2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
index a5eef06c4226..f13cde4321b1 100644
--- a/drivers/dma-buf/heaps/Kconfig
+++ b/drivers/dma-buf/heaps/Kconfig
@@ -1,6 +1,7 @@
config DMABUF_HEAPS_SYSTEM
bool "DMA-BUF System Heap"
depends on DMABUF_HEAPS
+ select PAGE_POOL
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 882a632e9bb7..9f57b4c8ae69 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -20,6 +20,7 @@
#include <linux/scatterlist.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
+#include <net/page_pool.h>

struct dma_heap *sys_heap;

@@ -46,6 +47,7 @@ struct dma_heap_attachment {
static gfp_t order_flags[] = {HIGH_ORDER_GFP, LOW_ORDER_GFP, LOW_ORDER_GFP};
static const unsigned int orders[] = {8, 4, 0};
#define NUM_ORDERS ARRAY_SIZE(orders)
+struct page_pool *pools[NUM_ORDERS];

static struct sg_table *dup_sg_table(struct sg_table *table)
{
@@ -264,13 +266,17 @@ static void system_heap_dma_buf_release(struct
dma_buf *dmabuf)
struct system_heap_buffer *buffer = dmabuf->priv;
struct sg_table *table;
struct scatterlist *sg;
- int i;
+ int i, j;

table = &buffer->sg_table;
for_each_sg(table->sgl, sg, table->nents, i) {
struct page *page = sg_page(sg);

- __free_pages(page, compound_order(page));
+ for (j = 0; j < NUM_ORDERS; j++) {
+ if (compound_order(page) == orders[j])
+ break;
+ }
+ page_pool_put_full_page(pools[j], page, false);
}
sg_free_table(table);
kfree(buffer);
@@ -300,8 +306,7 @@ static struct page
*alloc_largest_available(unsigned long size,
continue;
if (max_order < orders[i])
continue;
-
- page = alloc_pages(order_flags[i], orders[i]);
+ page = page_pool_alloc_pages(pools[i], order_flags[i]);
if (!page)
continue;
return page;
@@ -406,6 +411,25 @@ static const struct dma_heap_ops system_heap_ops = {
static int system_heap_create(void)
{
struct dma_heap_export_info exp_info;
+ int i;
+
+ for (i = 0; i < NUM_ORDERS; i++) {
+ struct page_pool_params pp;
+
+ memset(&pp, 0, sizeof(pp));
+ pp.order = orders[i];
+ pp.dma_dir = DMA_BIDIRECTIONAL;

Hey John,

Correct me if I'm wrong, but I think that in order for pp.dma_dir to be used in either page_pool_alloc_pages() or page_pool_put_full_page(), we need to at least have PP_FLAG_DMA_MAP set (to have page_pool_dma_sync_for_device() called, PP_FLAG_DMA_SYNC_DEV should also be set I think). I think you'd also need to to have pp->dev set. Are we setting dma_dir with the intention of doing the necessary CMOs before we start using the page?

Thanks,

Chris.

+ pools[i] = page_pool_create(&pp);
+
+ if (IS_ERR(pools[i])) {
+ int j;
+
+ pr_err("%s: page pool creation failed!\n", __func__);
+ for (j = 0; j < i; j++)
+ page_pool_destroy(pools[j]);
+ return PTR_ERR(pools[i]);
+ }
+ }

exp_info.name = "system";
exp_info.ops = &system_heap_ops;

This is cool, I didn't know about this pooling code under /net/core.
Nice and compact.

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