diff mbox series

[v2,2/3] dma-buf: system_heap: Add pagepool support to system heap

Message ID 20210123034655.102813-2-john.stultz@linaro.org (mailing list archive)
State New, archived
Headers show
Series [v2,1/3] dma-buf: heaps: Add deferred-free-helper library code | expand

Commit Message

John Stultz Jan. 23, 2021, 3:46 a.m. UTC
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: Daniel Vetter <daniel@ffwll.ch>
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>
---
v2:
* Fix build issue caused by selecting PAGE_POOL w/o NET
  as Reported-by: kernel test robot <lkp@intel.com>
---
 drivers/dma-buf/heaps/Kconfig       |  2 +
 drivers/dma-buf/heaps/system_heap.c | 68 +++++++++++++++++++++++++++--
 2 files changed, 66 insertions(+), 4 deletions(-)

Comments

Daniel Mentz Jan. 27, 2021, 8:21 p.m. UTC | #1
On Fri, Jan 22, 2021 at 7:47 PM John Stultz <john.stultz@linaro.org> wrote:
> +static int system_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot)
> +{
> +       void *addr = vmap(pages, num, VM_MAP, pgprot);
> +
> +       if (!addr)
> +               return -ENOMEM;
> +       memset(addr, 0, PAGE_SIZE * num);
> +       vunmap(addr);
> +       return 0;
> +}

I thought that vmap/vunmap are expensive, and I am wondering if
there's a faster way that avoids vmap.

How about lifting this code from lib/iov_iter.c
static void memzero_page(struct page *page, size_t offset, size_t len)
{
        char *addr = kmap_atomic(page);
        memset(addr + offset, 0, len);
        kunmap_atomic(addr);
}

Or what about lifting that code from the old ion_cma_heap.c

if (PageHighMem(pages)) {
        unsigned long nr_clear_pages = nr_pages;
        struct page *page = pages;

        while (nr_clear_pages > 0) {
                void *vaddr = kmap_atomic(page);

                memset(vaddr, 0, PAGE_SIZE);
                kunmap_atomic(vaddr);
                page++;
                nr_clear_pages--;
        }
} else {
        memset(page_address(pages), 0, size);
}
John Stultz Jan. 28, 2021, 5:10 a.m. UTC | #2
On Wed, Jan 27, 2021 at 12:21 PM Daniel Mentz <danielmentz@google.com> wrote:
>
> On Fri, Jan 22, 2021 at 7:47 PM John Stultz <john.stultz@linaro.org> wrote:
> > +static int system_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot)
> > +{
> > +       void *addr = vmap(pages, num, VM_MAP, pgprot);
> > +
> > +       if (!addr)
> > +               return -ENOMEM;
> > +       memset(addr, 0, PAGE_SIZE * num);
> > +       vunmap(addr);
> > +       return 0;
> > +}
>
> I thought that vmap/vunmap are expensive, and I am wondering if
> there's a faster way that avoids vmap.
>
> How about lifting this code from lib/iov_iter.c
> static void memzero_page(struct page *page, size_t offset, size_t len)
> {
>         char *addr = kmap_atomic(page);
>         memset(addr + offset, 0, len);
>         kunmap_atomic(addr);
> }
>
> Or what about lifting that code from the old ion_cma_heap.c
>
> if (PageHighMem(pages)) {
>         unsigned long nr_clear_pages = nr_pages;
>         struct page *page = pages;
>
>         while (nr_clear_pages > 0) {
>                 void *vaddr = kmap_atomic(page);
>
>                 memset(vaddr, 0, PAGE_SIZE);
>                 kunmap_atomic(vaddr);
>                 page++;
>                 nr_clear_pages--;
>         }
> } else {
>         memset(page_address(pages), 0, size);
> }

Though, this last memset only works since CMA is contiguous, so it
probably needs to always do the kmap_atomic for each page, right?

I'm still a little worried if this is right, as the current
implementation with the vmap comes from the old ion_heap_sglist_zero
logic, which similarly tries to batch the vmaps  32 pages at at time,
but I'll give it a try.

thanks
-john
Daniel Mentz Jan. 28, 2021, 7:04 a.m. UTC | #3
On Wed, Jan 27, 2021 at 9:10 PM John Stultz <john.stultz@linaro.org> wrote:
>
> On Wed, Jan 27, 2021 at 12:21 PM Daniel Mentz <danielmentz@google.com> wrote:
> >
> > On Fri, Jan 22, 2021 at 7:47 PM John Stultz <john.stultz@linaro.org> wrote:
> > > +static int system_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot)
> > > +{
> > > +       void *addr = vmap(pages, num, VM_MAP, pgprot);
> > > +
> > > +       if (!addr)
> > > +               return -ENOMEM;
> > > +       memset(addr, 0, PAGE_SIZE * num);
> > > +       vunmap(addr);
> > > +       return 0;
> > > +}
> >
> > I thought that vmap/vunmap are expensive, and I am wondering if
> > there's a faster way that avoids vmap.
> >
> > How about lifting this code from lib/iov_iter.c
> > static void memzero_page(struct page *page, size_t offset, size_t len)
> > {
> >         char *addr = kmap_atomic(page);
> >         memset(addr + offset, 0, len);
> >         kunmap_atomic(addr);
> > }
> >
> > Or what about lifting that code from the old ion_cma_heap.c
> >
> > if (PageHighMem(pages)) {
> >         unsigned long nr_clear_pages = nr_pages;
> >         struct page *page = pages;
> >
> >         while (nr_clear_pages > 0) {
> >                 void *vaddr = kmap_atomic(page);
> >
> >                 memset(vaddr, 0, PAGE_SIZE);
> >                 kunmap_atomic(vaddr);
> >                 page++;
> >                 nr_clear_pages--;
> >         }
> > } else {
> >         memset(page_address(pages), 0, size);
> > }
>
> Though, this last memset only works since CMA is contiguous, so it
> probably needs to always do the kmap_atomic for each page, right?

Yeah, but with the system heap page pool, some of these pages might be
64KB or 1MB large. kmap_atomic(page) just maps to page_address(page)
in most cases. I think iterating over all pages individually in this
manner might still be faster than using vmap.

>
> I'm still a little worried if this is right, as the current
> implementation with the vmap comes from the old ion_heap_sglist_zero
> logic, which similarly tries to batch the vmaps  32 pages at at time,
> but I'll give it a try.
diff mbox series

Patch

diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
index ecf65204f714..748e840e6edd 100644
--- a/drivers/dma-buf/heaps/Kconfig
+++ b/drivers/dma-buf/heaps/Kconfig
@@ -4,6 +4,8 @@  config DMABUF_HEAPS_DEFERRED_FREE
 config DMABUF_HEAPS_SYSTEM
 	bool "DMA-BUF System Heap"
 	depends on DMABUF_HEAPS
+	select NET
+	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 17e0e9a68baf..885e30894b77 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>
 
 static struct dma_heap *sys_heap;
 
@@ -53,6 +54,7 @@  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)
 {
@@ -281,18 +283,59 @@  static void system_heap_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
 	dma_buf_map_clear(map);
 }
 
+static int system_heap_clear_pages(struct page **pages, int num, pgprot_t pgprot)
+{
+	void *addr = vmap(pages, num, VM_MAP, pgprot);
+
+	if (!addr)
+		return -ENOMEM;
+	memset(addr, 0, PAGE_SIZE * num);
+	vunmap(addr);
+	return 0;
+}
+
+static int system_heap_zero_buffer(struct system_heap_buffer *buffer)
+{
+	struct sg_table *sgt = &buffer->sg_table;
+	struct sg_page_iter piter;
+	struct page *pages[32];
+	int p = 0;
+	int ret = 0;
+
+	for_each_sgtable_page(sgt, &piter, 0) {
+		pages[p++] = sg_page_iter_page(&piter);
+		if (p == ARRAY_SIZE(pages)) {
+			ret = system_heap_clear_pages(pages, p, PAGE_KERNEL);
+			if (ret)
+				return ret;
+			p = 0;
+		}
+	}
+	if (p)
+		ret = system_heap_clear_pages(pages, p, PAGE_KERNEL);
+
+	return ret;
+}
+
 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;
+
+	/* Zero the buffer pages before adding back to the pool */
+	system_heap_zero_buffer(buffer);
 
 	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);
@@ -322,8 +365,7 @@  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;
@@ -428,6 +470,24 @@  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];
+		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;