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

[Chris Goldsworthy <cgoldswo@codeaurora.org>]

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@linaro.org>
>> Cc: Liam Mark <lmark@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: 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>
>> ---
>>  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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