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-rw-r--r--include/net/page_pool/helpers.h230
1 files changed, 196 insertions, 34 deletions
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 94231533a369..4ebd544ae977 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -8,23 +8,46 @@
/**
* DOC: page_pool allocator
*
- * The page_pool allocator is optimized for the XDP mode that
- * uses one frame per-page, but it can fallback on the
- * regular page allocator APIs.
- *
- * Basic use involves replacing alloc_pages() calls with the
- * page_pool_alloc_pages() call. Drivers should use
- * page_pool_dev_alloc_pages() replacing dev_alloc_pages().
- *
- * API keeps track of in-flight pages, in order to let API user know
- * when it is safe to free a page_pool object. Thus, API users
- * must call page_pool_put_page() to free the page, or attach
- * the page to a page_pool-aware objects like skbs marked with
+ * The page_pool allocator is optimized for recycling page or page fragment used
+ * by skb packet and xdp frame.
+ *
+ * Basic use involves replacing and alloc_pages() calls with page_pool_alloc(),
+ * which allocate memory with or without page splitting depending on the
+ * requested memory size.
+ *
+ * If the driver knows that it always requires full pages or its allocations are
+ * always smaller than half a page, it can use one of the more specific API
+ * calls:
+ *
+ * 1. page_pool_alloc_pages(): allocate memory without page splitting when
+ * driver knows that the memory it need is always bigger than half of the page
+ * allocated from page pool. There is no cache line dirtying for 'struct page'
+ * when a page is recycled back to the page pool.
+ *
+ * 2. page_pool_alloc_frag(): allocate memory with page splitting when driver
+ * knows that the memory it need is always smaller than or equal to half of the
+ * page allocated from page pool. Page splitting enables memory saving and thus
+ * avoids TLB/cache miss for data access, but there also is some cost to
+ * implement page splitting, mainly some cache line dirtying/bouncing for
+ * 'struct page' and atomic operation for page->pp_frag_count.
+ *
+ * The API keeps track of in-flight pages, in order to let API users know when
+ * it is safe to free a page_pool object, the API users must call
+ * page_pool_put_page() or page_pool_free_va() to free the page_pool object, or
+ * attach the page_pool object to a page_pool-aware object like skbs marked with
* skb_mark_for_recycle().
*
- * API user must call page_pool_put_page() once on a page, as it
- * will either recycle the page, or in case of refcnt > 1, it will
- * release the DMA mapping and in-flight state accounting.
+ * page_pool_put_page() may be called multi times on the same page if a page is
+ * split into multi fragments. For the last fragment, it will either recycle the
+ * page, or in case of page->_refcount > 1, it will release the DMA mapping and
+ * in-flight state accounting.
+ *
+ * dma_sync_single_range_for_device() is only called for the last fragment when
+ * page_pool is created with PP_FLAG_DMA_SYNC_DEV flag, so it depends on the
+ * last freed fragment to do the sync_for_device operation for all fragments in
+ * the same page when a page is split, the API user must setup pool->p.max_len
+ * and pool->p.offset correctly and ensure that page_pool_put_page() is called
+ * with dma_sync_size being -1 for fragment API.
*/
#ifndef _NET_PAGE_POOL_HELPERS_H
#define _NET_PAGE_POOL_HELPERS_H
@@ -73,6 +96,17 @@ static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
return page_pool_alloc_pages(pool, gfp);
}
+/**
+ * page_pool_dev_alloc_frag() - allocate a page fragment.
+ * @pool: pool from which to allocate
+ * @offset: offset to the allocated page
+ * @size: requested size
+ *
+ * Get a page fragment from the page allocator or page_pool caches.
+ *
+ * Return:
+ * Return allocated page fragment, otherwise return NULL.
+ */
static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
unsigned int *offset,
unsigned int size)
@@ -82,6 +116,91 @@ static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
return page_pool_alloc_frag(pool, offset, size, gfp);
}
+static inline struct page *page_pool_alloc(struct page_pool *pool,
+ unsigned int *offset,
+ unsigned int *size, gfp_t gfp)
+{
+ unsigned int max_size = PAGE_SIZE << pool->p.order;
+ struct page *page;
+
+ if ((*size << 1) > max_size) {
+ *size = max_size;
+ *offset = 0;
+ return page_pool_alloc_pages(pool, gfp);
+ }
+
+ page = page_pool_alloc_frag(pool, offset, *size, gfp);
+ if (unlikely(!page))
+ return NULL;
+
+ /* There is very likely not enough space for another fragment, so append
+ * the remaining size to the current fragment to avoid truesize
+ * underestimate problem.
+ */
+ if (pool->frag_offset + *size > max_size) {
+ *size = max_size - *offset;
+ pool->frag_offset = max_size;
+ }
+
+ return page;
+}
+
+/**
+ * page_pool_dev_alloc() - allocate a page or a page fragment.
+ * @pool: pool from which to allocate
+ * @offset: offset to the allocated page
+ * @size: in as the requested size, out as the allocated size
+ *
+ * Get a page or a page fragment from the page allocator or page_pool caches
+ * depending on the requested size in order to allocate memory with least memory
+ * utilization and performance penalty.
+ *
+ * Return:
+ * Return allocated page or page fragment, otherwise return NULL.
+ */
+static inline struct page *page_pool_dev_alloc(struct page_pool *pool,
+ unsigned int *offset,
+ unsigned int *size)
+{
+ gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
+
+ return page_pool_alloc(pool, offset, size, gfp);
+}
+
+static inline void *page_pool_alloc_va(struct page_pool *pool,
+ unsigned int *size, gfp_t gfp)
+{
+ unsigned int offset;
+ struct page *page;
+
+ /* Mask off __GFP_HIGHMEM to ensure we can use page_address() */
+ page = page_pool_alloc(pool, &offset, size, gfp & ~__GFP_HIGHMEM);
+ if (unlikely(!page))
+ return NULL;
+
+ return page_address(page) + offset;
+}
+
+/**
+ * page_pool_dev_alloc_va() - allocate a page or a page fragment and return its
+ * va.
+ * @pool: pool from which to allocate
+ * @size: in as the requested size, out as the allocated size
+ *
+ * This is just a thin wrapper around the page_pool_alloc() API, and
+ * it returns va of the allocated page or page fragment.
+ *
+ * Return:
+ * Return the va for the allocated page or page fragment, otherwise return NULL.
+ */
+static inline void *page_pool_dev_alloc_va(struct page_pool *pool,
+ unsigned int *size)
+{
+ gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
+
+ return page_pool_alloc_va(pool, size, gfp);
+}
+
/**
* page_pool_get_dma_dir() - Retrieve the stored DMA direction.
* @pool: pool from which page was allocated
@@ -115,28 +234,49 @@ static inline long page_pool_defrag_page(struct page *page, long nr)
long ret;
/* If nr == pp_frag_count then we have cleared all remaining
- * references to the page. No need to actually overwrite it, instead
- * we can leave this to be overwritten by the calling function.
+ * references to the page:
+ * 1. 'n == 1': no need to actually overwrite it.
+ * 2. 'n != 1': overwrite it with one, which is the rare case
+ * for pp_frag_count draining.
*
- * The main advantage to doing this is that an atomic_read is
- * generally a much cheaper operation than an atomic update,
- * especially when dealing with a page that may be partitioned
- * into only 2 or 3 pieces.
+ * The main advantage to doing this is that not only we avoid a atomic
+ * update, as an atomic_read is generally a much cheaper operation than
+ * an atomic update, especially when dealing with a page that may be
+ * partitioned into only 2 or 3 pieces; but also unify the pp_frag_count
+ * handling by ensuring all pages have partitioned into only 1 piece
+ * initially, and only overwrite it when the page is partitioned into
+ * more than one piece.
*/
- if (atomic_long_read(&page->pp_frag_count) == nr)
+ if (atomic_long_read(&page->pp_frag_count) == nr) {
+ /* As we have ensured nr is always one for constant case using
+ * the BUILD_BUG_ON(), only need to handle the non-constant case
+ * here for pp_frag_count draining, which is a rare case.
+ */
+ BUILD_BUG_ON(__builtin_constant_p(nr) && nr != 1);
+ if (!__builtin_constant_p(nr))
+ atomic_long_set(&page->pp_frag_count, 1);
+
return 0;
+ }
ret = atomic_long_sub_return(nr, &page->pp_frag_count);
WARN_ON(ret < 0);
+
+ /* We are the last user here too, reset pp_frag_count back to 1 to
+ * ensure all pages have been partitioned into 1 piece initially,
+ * this should be the rare case when the last two fragment users call
+ * page_pool_defrag_page() currently.
+ */
+ if (unlikely(!ret))
+ atomic_long_set(&page->pp_frag_count, 1);
+
return ret;
}
-static inline bool page_pool_is_last_frag(struct page_pool *pool,
- struct page *page)
+static inline bool page_pool_is_last_frag(struct page *page)
{
- /* If fragments aren't enabled or count is 0 we were the last user */
- return !(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
- (page_pool_defrag_page(page, 1) == 0);
+ /* If page_pool_defrag_page() returns 0, we were the last user */
+ return page_pool_defrag_page(page, 1) == 0;
}
/**
@@ -161,7 +301,7 @@ static inline void page_pool_put_page(struct page_pool *pool,
* allow registering MEM_TYPE_PAGE_POOL, but shield linker.
*/
#ifdef CONFIG_PAGE_POOL
- if (!page_pool_is_last_frag(pool, page))
+ if (!page_pool_is_last_frag(page))
return;
page_pool_put_defragged_page(pool, page, dma_sync_size, allow_direct);
@@ -197,10 +337,24 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
page_pool_put_full_page(pool, page, true);
}
-#define PAGE_POOL_DMA_USE_PP_FRAG_COUNT \
+#define PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA \
(sizeof(dma_addr_t) > sizeof(unsigned long))
/**
+ * page_pool_free_va() - free a va into the page_pool
+ * @pool: pool from which va was allocated
+ * @va: va to be freed
+ * @allow_direct: freed by the consumer, allow lockless caching
+ *
+ * Free a va allocated from page_pool_allo_va().
+ */
+static inline void page_pool_free_va(struct page_pool *pool, void *va,
+ bool allow_direct)
+{
+ page_pool_put_page(pool, virt_to_head_page(va), -1, allow_direct);
+}
+
+/**
* page_pool_get_dma_addr() - Retrieve the stored DMA address.
* @page: page allocated from a page pool
*
@@ -211,17 +365,25 @@ static inline dma_addr_t page_pool_get_dma_addr(struct page *page)
{
dma_addr_t ret = page->dma_addr;
- if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
- ret |= (dma_addr_t)page->dma_addr_upper << 16 << 16;
+ if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA)
+ ret <<= PAGE_SHIFT;
return ret;
}
-static inline void page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
+static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
{
+ if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
+ page->dma_addr = addr >> PAGE_SHIFT;
+
+ /* We assume page alignment to shave off bottom bits,
+ * if this "compression" doesn't work we need to drop.
+ */
+ return addr != (dma_addr_t)page->dma_addr << PAGE_SHIFT;
+ }
+
page->dma_addr = addr;
- if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
- page->dma_addr_upper = upper_32_bits(addr);
+ return false;
}
static inline bool page_pool_put(struct page_pool *pool)