![Jesper Dangaard Brouer](/assets/img/avatar_default.png)
When sending an xdp_frame through xdp_do_redirect call, then error cases can happen where the xdp_frame needs to be dropped, and returning an -errno code isn't sufficient/possible any-longer (e.g. for cpumap case). This is already fully supported, by simply calling xdp_return_frame. This patch is an optimization, which provides xdp_return_frame_rx_napi, which is a faster variant for these error cases. It take advantage of the protection provided by XDP RX running under NAPI protection. This change is mostly relevant for drivers using the page_pool allocator as it can take advantage of this. (Tested with mlx5). Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
145 lines
4.4 KiB
C
145 lines
4.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0
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*
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* page_pool.h
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* Author: Jesper Dangaard Brouer <netoptimizer@brouer.com>
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* Copyright (C) 2016 Red Hat, Inc.
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*/
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/**
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* DOC: page_pool allocator
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*
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* This page_pool allocator is optimized for the XDP mode that
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* uses one-frame-per-page, but have fallbacks that act like the
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* regular page allocator APIs.
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*
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* Basic use involve replacing alloc_pages() calls with the
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* page_pool_alloc_pages() call. Drivers should likely use
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* page_pool_dev_alloc_pages() replacing dev_alloc_pages().
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*
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* If page_pool handles DMA mapping (use page->private), then API user
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* is responsible for invoking page_pool_put_page() once. In-case of
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* elevated refcnt, the DMA state is released, assuming other users of
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* the page will eventually call put_page().
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*
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* If no DMA mapping is done, then it can act as shim-layer that
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* fall-through to alloc_page. As no state is kept on the page, the
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* regular put_page() call is sufficient.
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*/
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#ifndef _NET_PAGE_POOL_H
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#define _NET_PAGE_POOL_H
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#include <linux/mm.h> /* Needed by ptr_ring */
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#include <linux/ptr_ring.h>
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#include <linux/dma-direction.h>
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#define PP_FLAG_DMA_MAP 1 /* Should page_pool do the DMA map/unmap */
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#define PP_FLAG_ALL PP_FLAG_DMA_MAP
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/*
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* Fast allocation side cache array/stack
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*
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* The cache size and refill watermark is related to the network
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* use-case. The NAPI budget is 64 packets. After a NAPI poll the RX
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* ring is usually refilled and the max consumed elements will be 64,
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* thus a natural max size of objects needed in the cache.
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*
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* Keeping room for more objects, is due to XDP_DROP use-case. As
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* XDP_DROP allows the opportunity to recycle objects directly into
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* this array, as it shares the same softirq/NAPI protection. If
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* cache is already full (or partly full) then the XDP_DROP recycles
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* would have to take a slower code path.
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*/
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#define PP_ALLOC_CACHE_SIZE 128
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#define PP_ALLOC_CACHE_REFILL 64
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struct pp_alloc_cache {
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u32 count;
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void *cache[PP_ALLOC_CACHE_SIZE];
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};
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struct page_pool_params {
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unsigned int flags;
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unsigned int order;
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unsigned int pool_size;
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int nid; /* Numa node id to allocate from pages from */
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struct device *dev; /* device, for DMA pre-mapping purposes */
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enum dma_data_direction dma_dir; /* DMA mapping direction */
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};
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struct page_pool {
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struct rcu_head rcu;
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struct page_pool_params p;
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/*
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* Data structure for allocation side
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*
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* Drivers allocation side usually already perform some kind
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* of resource protection. Piggyback on this protection, and
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* require driver to protect allocation side.
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*
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* For NIC drivers this means, allocate a page_pool per
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* RX-queue. As the RX-queue is already protected by
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* Softirq/BH scheduling and napi_schedule. NAPI schedule
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* guarantee that a single napi_struct will only be scheduled
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* on a single CPU (see napi_schedule).
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*/
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struct pp_alloc_cache alloc ____cacheline_aligned_in_smp;
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/* Data structure for storing recycled pages.
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*
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* Returning/freeing pages is more complicated synchronization
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* wise, because free's can happen on remote CPUs, with no
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* association with allocation resource.
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*
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* Use ptr_ring, as it separates consumer and producer
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* effeciently, it a way that doesn't bounce cache-lines.
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*
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* TODO: Implement bulk return pages into this structure.
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*/
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struct ptr_ring ring;
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};
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struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp);
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static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
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{
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gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
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return page_pool_alloc_pages(pool, gfp);
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}
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struct page_pool *page_pool_create(const struct page_pool_params *params);
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void page_pool_destroy(struct page_pool *pool);
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/* Never call this directly, use helpers below */
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void __page_pool_put_page(struct page_pool *pool,
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struct page *page, bool allow_direct);
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static inline void page_pool_put_page(struct page_pool *pool,
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struct page *page, bool allow_direct)
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{
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/* When page_pool isn't compiled-in, net/core/xdp.c doesn't
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* allow registering MEM_TYPE_PAGE_POOL, but shield linker.
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*/
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#ifdef CONFIG_PAGE_POOL
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__page_pool_put_page(pool, page, allow_direct);
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#endif
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}
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/* Very limited use-cases allow recycle direct */
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static inline void page_pool_recycle_direct(struct page_pool *pool,
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struct page *page)
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{
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__page_pool_put_page(pool, page, true);
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}
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static inline bool is_page_pool_compiled_in(void)
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{
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#ifdef CONFIG_PAGE_POOL
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return true;
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#else
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return false;
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#endif
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}
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#endif /* _NET_PAGE_POOL_H */
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