page_pool: refurbish version of page_pool code
Need a fast page recycle mechanism for ndo_xdp_xmit API for returning pages on DMA-TX completion time, which have good cross CPU performance, given DMA-TX completion time can happen on a remote CPU. Refurbish my page_pool code, that was presented[1] at MM-summit 2016. Adapted page_pool code to not depend the page allocator and integration into struct page. The DMA mapping feature is kept, even-though it will not be activated/used in this patchset. [1] http://people.netfilter.org/hawk/presentations/MM-summit2016/generic_page_pool_mm_summit2016.pdf V2: Adjustments requested by Tariq - Changed page_pool_create return codes, don't return NULL, only ERR_PTR, as this simplifies err handling in drivers. V4: many small improvements and cleanups - Add DOC comment section, that can be used by kernel-doc - Improve fallback mode, to work better with refcnt based recycling e.g. remove a WARN as pointed out by Tariq e.g. quicker fallback if ptr_ring is empty. V5: Fixed SPDX license as pointed out by Alexei V6: Adjustments requested by Eric Dumazet - Adjust ____cacheline_aligned_in_smp usage/placement - Move rcu_head in struct page_pool - Free pages quicker on destroy, minimize resources delayed an RCU period - Remove code for forward/backward compat ABI interface V8: Issues found by kbuild test robot - Address sparse should be static warnings - Only compile+link when a driver use/select page_pool, mlx5 selects CONFIG_PAGE_POOL, although its first used in two patches Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jesper Dangaard Brouer
David S. Miller
parent
8d5d885275
commit
ff7d6b27f8
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@ -30,6 +30,7 @@ config MLX5_CORE_EN
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bool "Mellanox Technologies ConnectX-4 Ethernet support"
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depends on NETDEVICES && ETHERNET && INET && PCI && MLX5_CORE
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depends on IPV6=y || IPV6=n || MLX5_CORE=m
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select PAGE_POOL
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default n
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---help---
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Ethernet support in Mellanox Technologies ConnectX-4 NIC.
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@ -0,0 +1,129 @@
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/* 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, struct page *page)
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{
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__page_pool_put_page(pool, page, false);
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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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#endif /* _NET_PAGE_POOL_H */
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@ -423,6 +423,9 @@ config MAY_USE_DEVLINK
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on MAY_USE_DEVLINK to ensure they do not cause link errors when
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devlink is a loadable module and the driver using it is built-in.
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config PAGE_POOL
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bool
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endif # if NET
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# Used by archs to tell that they support BPF JIT compiler plus which flavour.
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@ -14,6 +14,7 @@ obj-y += dev.o ethtool.o dev_addr_lists.o dst.o netevent.o \
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fib_notifier.o xdp.o
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obj-y += net-sysfs.o
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obj-$(CONFIG_PAGE_POOL) += page_pool.o
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obj-$(CONFIG_PROC_FS) += net-procfs.o
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obj-$(CONFIG_NET_PKTGEN) += pktgen.o
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obj-$(CONFIG_NETPOLL) += netpoll.o
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@ -0,0 +1,317 @@
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/* SPDX-License-Identifier: GPL-2.0
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*
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* page_pool.c
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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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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <net/page_pool.h>
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#include <linux/dma-direction.h>
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#include <linux/dma-mapping.h>
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#include <linux/page-flags.h>
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#include <linux/mm.h> /* for __put_page() */
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static int page_pool_init(struct page_pool *pool,
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const struct page_pool_params *params)
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{
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unsigned int ring_qsize = 1024; /* Default */
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memcpy(&pool->p, params, sizeof(pool->p));
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/* Validate only known flags were used */
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if (pool->p.flags & ~(PP_FLAG_ALL))
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return -EINVAL;
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if (pool->p.pool_size)
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ring_qsize = pool->p.pool_size;
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/* Sanity limit mem that can be pinned down */
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if (ring_qsize > 32768)
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return -E2BIG;
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/* DMA direction is either DMA_FROM_DEVICE or DMA_BIDIRECTIONAL.
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* DMA_BIDIRECTIONAL is for allowing page used for DMA sending,
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* which is the XDP_TX use-case.
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*/
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if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
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(pool->p.dma_dir != DMA_BIDIRECTIONAL))
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return -EINVAL;
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if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0)
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return -ENOMEM;
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return 0;
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}
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struct page_pool *page_pool_create(const struct page_pool_params *params)
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{
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struct page_pool *pool;
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int err = 0;
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pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, params->nid);
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if (!pool)
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return ERR_PTR(-ENOMEM);
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err = page_pool_init(pool, params);
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if (err < 0) {
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pr_warn("%s() gave up with errno %d\n", __func__, err);
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kfree(pool);
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return ERR_PTR(err);
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}
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return pool;
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}
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EXPORT_SYMBOL(page_pool_create);
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/* fast path */
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static struct page *__page_pool_get_cached(struct page_pool *pool)
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{
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struct ptr_ring *r = &pool->ring;
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struct page *page;
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/* Quicker fallback, avoid locks when ring is empty */
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if (__ptr_ring_empty(r))
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return NULL;
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/* Test for safe-context, caller should provide this guarantee */
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if (likely(in_serving_softirq())) {
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if (likely(pool->alloc.count)) {
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/* Fast-path */
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page = pool->alloc.cache[--pool->alloc.count];
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return page;
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}
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/* Slower-path: Alloc array empty, time to refill
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*
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* Open-coded bulk ptr_ring consumer.
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*
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* Discussion: the ring consumer lock is not really
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* needed due to the softirq/NAPI protection, but
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* later need the ability to reclaim pages on the
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* ring. Thus, keeping the locks.
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*/
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spin_lock(&r->consumer_lock);
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while ((page = __ptr_ring_consume(r))) {
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if (pool->alloc.count == PP_ALLOC_CACHE_REFILL)
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break;
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pool->alloc.cache[pool->alloc.count++] = page;
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}
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spin_unlock(&r->consumer_lock);
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return page;
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}
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/* Slow-path: Get page from locked ring queue */
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page = ptr_ring_consume(&pool->ring);
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return page;
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}
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/* slow path */
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noinline
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static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
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gfp_t _gfp)
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{
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struct page *page;
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gfp_t gfp = _gfp;
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dma_addr_t dma;
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/* We could always set __GFP_COMP, and avoid this branch, as
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* prep_new_page() can handle order-0 with __GFP_COMP.
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*/
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if (pool->p.order)
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gfp |= __GFP_COMP;
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/* FUTURE development:
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*
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* Current slow-path essentially falls back to single page
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* allocations, which doesn't improve performance. This code
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* need bulk allocation support from the page allocator code.
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*/
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/* Cache was empty, do real allocation */
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page = alloc_pages_node(pool->p.nid, gfp, pool->p.order);
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if (!page)
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return NULL;
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if (!(pool->p.flags & PP_FLAG_DMA_MAP))
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goto skip_dma_map;
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/* Setup DMA mapping: use page->private for DMA-addr
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* This mapping is kept for lifetime of page, until leaving pool.
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*/
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dma = dma_map_page(pool->p.dev, page, 0,
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(PAGE_SIZE << pool->p.order),
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pool->p.dma_dir);
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if (dma_mapping_error(pool->p.dev, dma)) {
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put_page(page);
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return NULL;
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}
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set_page_private(page, dma); /* page->private = dma; */
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skip_dma_map:
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/* When page just alloc'ed is should/must have refcnt 1. */
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return page;
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}
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/* For using page_pool replace: alloc_pages() API calls, but provide
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* synchronization guarantee for allocation side.
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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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{
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struct page *page;
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/* Fast-path: Get a page from cache */
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page = __page_pool_get_cached(pool);
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if (page)
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return page;
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/* Slow-path: cache empty, do real allocation */
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page = __page_pool_alloc_pages_slow(pool, gfp);
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return page;
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}
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EXPORT_SYMBOL(page_pool_alloc_pages);
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/* Cleanup page_pool state from page */
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static void __page_pool_clean_page(struct page_pool *pool,
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struct page *page)
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{
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if (!(pool->p.flags & PP_FLAG_DMA_MAP))
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return;
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/* DMA unmap */
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dma_unmap_page(pool->p.dev, page_private(page),
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PAGE_SIZE << pool->p.order, pool->p.dma_dir);
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set_page_private(page, 0);
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}
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/* Return a page to the page allocator, cleaning up our state */
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static void __page_pool_return_page(struct page_pool *pool, struct page *page)
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{
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__page_pool_clean_page(pool, page);
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put_page(page);
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/* An optimization would be to call __free_pages(page, pool->p.order)
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* knowing page is not part of page-cache (thus avoiding a
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* __page_cache_release() call).
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*/
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}
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static bool __page_pool_recycle_into_ring(struct page_pool *pool,
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struct page *page)
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{
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int ret;
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/* BH protection not needed if current is serving softirq */
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if (in_serving_softirq())
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ret = ptr_ring_produce(&pool->ring, page);
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else
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ret = ptr_ring_produce_bh(&pool->ring, page);
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return (ret == 0) ? true : false;
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}
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/* Only allow direct recycling in special circumstances, into the
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* alloc side cache. E.g. during RX-NAPI processing for XDP_DROP use-case.
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*
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* Caller must provide appropriate safe context.
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*/
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static bool __page_pool_recycle_direct(struct page *page,
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struct page_pool *pool)
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{
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if (unlikely(pool->alloc.count == PP_ALLOC_CACHE_SIZE))
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return false;
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/* Caller MUST have verified/know (page_ref_count(page) == 1) */
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pool->alloc.cache[pool->alloc.count++] = page;
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return true;
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}
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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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{
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/* This allocator is optimized for the XDP mode that uses
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* 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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* refcnt == 1 means page_pool owns page, and can recycle it.
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*/
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if (likely(page_ref_count(page) == 1)) {
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/* Read barrier done in page_ref_count / READ_ONCE */
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if (allow_direct && in_serving_softirq())
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if (__page_pool_recycle_direct(page, pool))
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return;
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if (!__page_pool_recycle_into_ring(pool, page)) {
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/* Cache full, fallback to free pages */
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__page_pool_return_page(pool, page);
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}
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return;
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}
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/* Fallback/non-XDP mode: API user have elevated refcnt.
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*
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* Many drivers split up the page into fragments, and some
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* want to keep doing this to save memory and do refcnt based
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* recycling. Support this use case too, to ease drivers
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* switching between XDP/non-XDP.
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*
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* In-case page_pool maintains the DMA mapping, API user must
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* call page_pool_put_page once. In this elevated refcnt
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* case, the DMA is unmapped/released, as driver is likely
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* doing refcnt based recycle tricks, meaning another process
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* will be invoking put_page.
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*/
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__page_pool_clean_page(pool, page);
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put_page(page);
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}
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EXPORT_SYMBOL(__page_pool_put_page);
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static void __page_pool_empty_ring(struct page_pool *pool)
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{
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struct page *page;
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/* Empty recycle ring */
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while ((page = ptr_ring_consume(&pool->ring))) {
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/* Verify the refcnt invariant of cached pages */
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if (!(page_ref_count(page) == 1))
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pr_crit("%s() page_pool refcnt %d violation\n",
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__func__, page_ref_count(page));
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__page_pool_return_page(pool, page);
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}
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}
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static void __page_pool_destroy_rcu(struct rcu_head *rcu)
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{
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struct page_pool *pool;
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pool = container_of(rcu, struct page_pool, rcu);
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WARN(pool->alloc.count, "API usage violation");
|
||||
|
||||
__page_pool_empty_ring(pool);
|
||||
ptr_ring_cleanup(&pool->ring, NULL);
|
||||
kfree(pool);
|
||||
}
|
||||
|
||||
/* Cleanup and release resources */
|
||||
void page_pool_destroy(struct page_pool *pool)
|
||||
{
|
||||
struct page *page;
|
||||
|
||||
/* Empty alloc cache, assume caller made sure this is
|
||||
* no-longer in use, and page_pool_alloc_pages() cannot be
|
||||
* call concurrently.
|
||||
*/
|
||||
while (pool->alloc.count) {
|
||||
page = pool->alloc.cache[--pool->alloc.count];
|
||||
__page_pool_return_page(pool, page);
|
||||
}
|
||||
|
||||
/* No more consumers should exist, but producers could still
|
||||
* be in-flight.
|
||||
*/
|
||||
__page_pool_empty_ring(pool);
|
||||
|
||||
/* An xdp_mem_allocator can still ref page_pool pointer */
|
||||
call_rcu(&pool->rcu, __page_pool_destroy_rcu);
|
||||
}
|
||||
EXPORT_SYMBOL(page_pool_destroy);
|
||||
Loading…
Reference in New Issue