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/* SPDX-License-Identifier: GPL-2.0
* page_pool.h
* Author: Jesper Dangaard Brouer <>
* Copyright (C) 2016 Red Hat, Inc.
* DOC: page_pool allocator
* This page_pool allocator is optimized for the XDP mode that
* uses one-frame-per-page, but have fallbacks that act like the
* regular page allocator APIs.
* Basic use involve replacing alloc_pages() calls with the
* page_pool_alloc_pages() call. Drivers should likely use
* page_pool_dev_alloc_pages() replacing dev_alloc_pages().
* If page_pool handles DMA mapping (use page->private), then API user
* is responsible for invoking page_pool_put_page() once. In-case of
* elevated refcnt, the DMA state is released, assuming other users of
* the page will eventually call put_page().
* If no DMA mapping is done, then it can act as shim-layer that
* fall-through to alloc_page. As no state is kept on the page, the
* regular put_page() call is sufficient.
#ifndef _NET_PAGE_POOL_H
#define _NET_PAGE_POOL_H
#include <linux/mm.h> /* Needed by ptr_ring */
#include <linux/ptr_ring.h>
#include <linux/dma-direction.h>
#define PP_FLAG_DMA_MAP 1 /* Should page_pool do the DMA map/unmap */
* Fast allocation side cache array/stack
* The cache size and refill watermark is related to the network
* use-case. The NAPI budget is 64 packets. After a NAPI poll the RX
* ring is usually refilled and the max consumed elements will be 64,
* thus a natural max size of objects needed in the cache.
* Keeping room for more objects, is due to XDP_DROP use-case. As
* XDP_DROP allows the opportunity to recycle objects directly into
* this array, as it shares the same softirq/NAPI protection. If
* cache is already full (or partly full) then the XDP_DROP recycles
* would have to take a slower code path.
struct pp_alloc_cache {
u32 count;
void *cache[PP_ALLOC_CACHE_SIZE];
struct page_pool_params {
unsigned int flags;
unsigned int order;
unsigned int pool_size;
int nid; /* Numa node id to allocate from pages from */
struct device *dev; /* device, for DMA pre-mapping purposes */
enum dma_data_direction dma_dir; /* DMA mapping direction */
struct page_pool {
struct rcu_head rcu;
struct page_pool_params p;
* Data structure for allocation side
* Drivers allocation side usually already perform some kind
* of resource protection. Piggyback on this protection, and
* require driver to protect allocation side.
* For NIC drivers this means, allocate a page_pool per
* RX-queue. As the RX-queue is already protected by
* Softirq/BH scheduling and napi_schedule. NAPI schedule
* guarantee that a single napi_struct will only be scheduled
* on a single CPU (see napi_schedule).
struct pp_alloc_cache alloc ____cacheline_aligned_in_smp;
/* Data structure for storing recycled pages.
* Returning/freeing pages is more complicated synchronization
* wise, because free's can happen on remote CPUs, with no
* association with allocation resource.
* Use ptr_ring, as it separates consumer and producer
* effeciently, it a way that doesn't bounce cache-lines.
* TODO: Implement bulk return pages into this structure.
struct ptr_ring ring;
struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp);
static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
return page_pool_alloc_pages(pool, gfp);
struct page_pool *page_pool_create(const struct page_pool_params *params);
void page_pool_destroy(struct page_pool *pool);
/* Never call this directly, use helpers below */
void __page_pool_put_page(struct page_pool *pool,
struct page *page, bool allow_direct);
static inline void page_pool_put_page(struct page_pool *pool,
struct page *page, bool allow_direct)
/* When page_pool isn't compiled-in, net/core/xdp.c doesn't
* allow registering MEM_TYPE_PAGE_POOL, but shield linker.
__page_pool_put_page(pool, page, allow_direct);
/* Very limited use-cases allow recycle direct */
static inline void page_pool_recycle_direct(struct page_pool *pool,
struct page *page)
__page_pool_put_page(pool, page, true);
static inline bool is_page_pool_compiled_in(void)
return true;
return false;
#endif /* _NET_PAGE_POOL_H */