diff options
Diffstat (limited to 'include/net/page_pool/helpers.h')
| -rw-r--r-- | include/net/page_pool/helpers.h | 85 |
1 files changed, 47 insertions, 38 deletions
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h index 4ebd544ae977..1d397c1a0043 100644 --- a/include/net/page_pool/helpers.h +++ b/include/net/page_pool/helpers.h @@ -11,7 +11,7 @@ * 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(), + * Basic use involves replacing any alloc_pages() calls with page_pool_alloc(), * which allocate memory with or without page splitting depending on the * requested memory size. * @@ -29,7 +29,7 @@ * 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. + * 'struct page' and atomic operation for page->pp_ref_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 @@ -37,15 +37,15 @@ * attach the page_pool object to a page_pool-aware object like skbs marked with * skb_mark_for_recycle(). * - * 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. + * page_pool_put_page() may be called multiple times on the same page if a page + * is split into multiple 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 + * 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. */ @@ -55,16 +55,12 @@ #include <net/page_pool/types.h> #ifdef CONFIG_PAGE_POOL_STATS +/* Deprecated driver-facing API, use netlink instead */ int page_pool_ethtool_stats_get_count(void); u8 *page_pool_ethtool_stats_get_strings(u8 *data); u64 *page_pool_ethtool_stats_get(u64 *data, void *stats); -/* - * Drivers that wish to harvest page pool stats and report them to users - * (perhaps via ethtool, debugfs, or another mechanism) can allocate a - * struct page_pool_stats call page_pool_get_stats to get stats for the specified pool. - */ -bool page_pool_get_stats(struct page_pool *pool, +bool page_pool_get_stats(const struct page_pool *pool, struct page_pool_stats *stats); #else static inline int page_pool_ethtool_stats_get_count(void) @@ -214,69 +210,82 @@ inline enum dma_data_direction page_pool_get_dma_dir(struct page_pool *pool) return pool->p.dma_dir; } -/* pp_frag_count represents the number of writers who can update the page - * either by updating skb->data or via DMA mappings for the device. - * We can't rely on the page refcnt for that as we don't know who might be - * holding page references and we can't reliably destroy or sync DMA mappings - * of the fragments. +/** + * page_pool_fragment_page() - split a fresh page into fragments + * @page: page to split + * @nr: references to set + * + * pp_ref_count represents the number of outstanding references to the page, + * which will be freed using page_pool APIs (rather than page allocator APIs + * like put_page()). Such references are usually held by page_pool-aware + * objects like skbs marked for page pool recycling. * - * When pp_frag_count reaches 0 we can either recycle the page if the page - * refcnt is 1 or return it back to the memory allocator and destroy any - * mappings we have. + * This helper allows the caller to take (set) multiple references to a + * freshly allocated page. The page must be freshly allocated (have a + * pp_ref_count of 1). This is commonly done by drivers and + * "fragment allocators" to save atomic operations - either when they know + * upfront how many references they will need; or to take MAX references and + * return the unused ones with a single atomic dec(), instead of performing + * multiple atomic inc() operations. */ static inline void page_pool_fragment_page(struct page *page, long nr) { - atomic_long_set(&page->pp_frag_count, nr); + atomic_long_set(&page->pp_ref_count, nr); } -static inline long page_pool_defrag_page(struct page *page, long nr) +static inline long page_pool_unref_page(struct page *page, long nr) { long ret; - /* If nr == pp_frag_count then we have cleared all remaining + /* If nr == pp_ref_count then we have cleared all remaining * 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. + * for pp_ref_count draining. * * 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 + * referenced by only 2 or 3 users; but also unify the pp_ref_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_ref_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. + * here for pp_ref_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); + atomic_long_set(&page->pp_ref_count, 1); return 0; } - ret = atomic_long_sub_return(nr, &page->pp_frag_count); + ret = atomic_long_sub_return(nr, &page->pp_ref_count); WARN_ON(ret < 0); - /* We are the last user here too, reset pp_frag_count back to 1 to + /* We are the last user here too, reset pp_ref_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. + * page_pool_unref_page() currently. */ if (unlikely(!ret)) - atomic_long_set(&page->pp_frag_count, 1); + atomic_long_set(&page->pp_ref_count, 1); return ret; } -static inline bool page_pool_is_last_frag(struct page *page) +static inline void page_pool_ref_page(struct page *page) +{ + atomic_long_inc(&page->pp_ref_count); +} + +static inline bool page_pool_is_last_ref(struct page *page) { - /* If page_pool_defrag_page() returns 0, we were the last user */ - return page_pool_defrag_page(page, 1) == 0; + /* If page_pool_unref_page() returns 0, we were the last user */ + return page_pool_unref_page(page, 1) == 0; } /** @@ -301,10 +310,10 @@ 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(page)) + if (!page_pool_is_last_ref(page)) return; - page_pool_put_defragged_page(pool, page, dma_sync_size, allow_direct); + page_pool_put_unrefed_page(pool, page, dma_sync_size, allow_direct); #endif } |