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

[Chris Goldsworthy]

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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