new file mode 100644
@@ -0,0 +1,133 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * page_pool.h
+ * Author: Jesper Dangaard Brouer <netoptimizer@brouer.com>
+ * 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 */
+#define PP_FLAG_ALL PP_FLAG_DMA_MAP
+
+/*
+ * 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.
+ */
+#define PP_ALLOC_CACHE_SIZE 128
+#define PP_ALLOC_CACHE_REFILL 64
+struct pp_alloc_cache {
+ u32 count ____cacheline_aligned_in_smp;
+ void *cache[PP_ALLOC_CACHE_SIZE];
+};
+
+struct page_pool_params {
+ u32 size; /* caller sets size of struct */
+ unsigned int order;
+ unsigned long flags;
+ struct device *dev; /* device, for DMA pre-mapping purposes */
+ int nid; /* Numa node id to allocate from pages from */
+ enum dma_data_direction dma_dir; /* DMA mapping direction */
+ unsigned int pool_size;
+ char end_marker[0]; /* must be last struct member */
+};
+#define PAGE_POOL_PARAMS_SIZE offsetof(struct page_pool_params, end_marker)
+
+struct page_pool {
+ 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;
+
+ /* 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 rcu_head rcu;
+};
+
+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_rcu(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)
+{
+ __page_pool_put_page(pool, page, false);
+}
+/* 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);
+}
+
+#endif /* _NET_PAGE_POOL_H */
@@ -14,6 +14,7 @@ obj-y += dev.o ethtool.o dev_addr_lists.o dst.o netevent.o \
fib_notifier.o xdp.o
obj-y += net-sysfs.o
+obj-y += page_pool.o
obj-$(CONFIG_PROC_FS) += net-procfs.o
obj-$(CONFIG_NET_PKTGEN) += pktgen.o
obj-$(CONFIG_NETPOLL) += netpoll.o
new file mode 100644
@@ -0,0 +1,329 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * page_pool.c
+ * Author: Jesper Dangaard Brouer <netoptimizer@brouer.com>
+ * Copyright (C) 2016 Red Hat, Inc.
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+
+#include <net/page_pool.h>
+#include <linux/dma-direction.h>
+#include <linux/dma-mapping.h>
+#include <linux/page-flags.h>
+#include <linux/mm.h> /* for __put_page() */
+
+int page_pool_init(struct page_pool *pool,
+ const struct page_pool_params *params)
+{
+ int ring_qsize = 1024; /* Default */
+ int param_copy_sz;
+
+ if (!pool)
+ return -EFAULT;
+
+ /* Note, below struct compat code was primarily needed when
+ * page_pool code lived under MM-tree control, given mmots and
+ * net-next trees progress in very different rates.
+ *
+ * Allow kernel devel trees and driver to progress at different rates
+ */
+ param_copy_sz = PAGE_POOL_PARAMS_SIZE;
+ memset(&pool->p, 0, param_copy_sz);
+ if (params->size < param_copy_sz) {
+ /* Older module calling newer kernel, handled by only
+ * copying supplied size, and keep remaining params zero
+ */
+ param_copy_sz = params->size;
+ } else if (params->size > param_copy_sz) {
+ /* Newer module calling older kernel. Need to validate
+ * no new features were requested.
+ */
+ unsigned char *addr = (unsigned char *)params + param_copy_sz;
+ unsigned char *end = (unsigned char *)params + params->size;
+
+ for (; addr < end; addr++) {
+ if (*addr != 0)
+ return -E2BIG;
+ }
+ }
+ memcpy(&pool->p, params, param_copy_sz);
+
+ /* Validate only known flags were used */
+ if (pool->p.flags & ~(PP_FLAG_ALL))
+ return -EINVAL;
+
+ if (pool->p.pool_size)
+ ring_qsize = pool->p.pool_size;
+
+ if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0)
+ return -ENOMEM;
+
+ /* DMA direction is either DMA_FROM_DEVICE or DMA_BIDIRECTIONAL.
+ * DMA_BIDIRECTIONAL is for allowing page used for DMA sending,
+ * which is the XDP_TX use-case.
+ */
+ if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
+ (pool->p.dma_dir != DMA_BIDIRECTIONAL))
+ return -EINVAL;
+
+ return 0;
+}
+
+struct page_pool *page_pool_create(const struct page_pool_params *params)
+{
+ struct page_pool *pool;
+ int err = 0;
+
+ if (params->size < offsetof(struct page_pool_params, nid)) {
+ WARN(1, "Fix page_pool_params->size code\n");
+ return ERR_PTR(-EBADR);
+ }
+
+ pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, params->nid);
+ err = page_pool_init(pool, params);
+ if (err < 0) {
+ pr_warn("%s() gave up with errno %d\n", __func__, err);
+ kfree(pool);
+ return ERR_PTR(err);
+ }
+ return pool;
+}
+EXPORT_SYMBOL(page_pool_create);
+
+/* fast path */
+static struct page *__page_pool_get_cached(struct page_pool *pool)
+{
+ struct ptr_ring *r = &pool->ring;
+ struct page *page;
+
+ /* Quicker fallback, avoid locks when ring is empty */
+ if (__ptr_ring_empty(r))
+ return NULL;
+
+ /* Test for safe-context, caller should provide this guarantee */
+ if (likely(in_serving_softirq())) {
+ if (likely(pool->alloc.count)) {
+ /* Fast-path */
+ page = pool->alloc.cache[--pool->alloc.count];
+ return page;
+ }
+ /* Slower-path: Alloc array empty, time to refill
+ *
+ * Open-coded bulk ptr_ring consumer.
+ *
+ * Discussion: the ring consumer lock is not really
+ * needed due to the softirq/NAPI protection, but
+ * later need the ability to reclaim pages on the
+ * ring. Thus, keeping the locks.
+ */
+ spin_lock(&r->consumer_lock);
+ while ((page = __ptr_ring_consume(r))) {
+ if (pool->alloc.count == PP_ALLOC_CACHE_REFILL)
+ break;
+ pool->alloc.cache[pool->alloc.count++] = page;
+ }
+ spin_unlock(&r->consumer_lock);
+ return page;
+ }
+
+ /* Slow-path: Get page from locked ring queue */
+ page = ptr_ring_consume(&pool->ring);
+ return page;
+}
+
+/* slow path */
+noinline
+static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
+ gfp_t _gfp)
+{
+ struct page *page;
+ gfp_t gfp = _gfp;
+ dma_addr_t dma;
+
+ /* We could always set __GFP_COMP, and avoid this branch, as
+ * prep_new_page() can handle order-0 with __GFP_COMP.
+ */
+ if (pool->p.order)
+ gfp |= __GFP_COMP;
+
+ /* FUTURE development:
+ *
+ * Current slow-path essentially falls back to single page
+ * allocations, which doesn't improve performance. This code
+ * need bulk allocation support from the page allocator code.
+ */
+
+ /* Cache was empty, do real allocation */
+ page = alloc_pages_node(pool->p.nid, gfp, pool->p.order);
+ if (!page)
+ return NULL;
+
+ if (!(pool->p.flags & PP_FLAG_DMA_MAP))
+ goto skip_dma_map;
+
+ /* Setup DMA mapping: use page->private for DMA-addr
+ * This mapping is kept for lifetime of page, until leaving pool.
+ */
+ dma = dma_map_page(pool->p.dev, page, 0,
+ (PAGE_SIZE << pool->p.order),
+ pool->p.dma_dir);
+ if (dma_mapping_error(pool->p.dev, dma)) {
+ put_page(page);
+ return NULL;
+ }
+ set_page_private(page, dma); /* page->private = dma; */
+
+skip_dma_map:
+ /* When page just alloc'ed is should/must have refcnt 1. */
+ return page;
+}
+
+/* For using page_pool replace: alloc_pages() API calls, but provide
+ * synchronization guarantee for allocation side.
+ */
+struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp)
+{
+ struct page *page;
+
+ /* Fast-path: Get a page from cache */
+ page = __page_pool_get_cached(pool);
+ if (page)
+ return page;
+
+ /* Slow-path: cache empty, do real allocation */
+ page = __page_pool_alloc_pages_slow(pool, gfp);
+ return page;
+}
+EXPORT_SYMBOL(page_pool_alloc_pages);
+
+/* Cleanup page_pool state from page */
+static void __page_pool_clean_page(struct page_pool *pool,
+ struct page *page)
+{
+ if (!(pool->p.flags & PP_FLAG_DMA_MAP))
+ return;
+
+ /* DMA unmap */
+ dma_unmap_page(pool->p.dev, page_private(page),
+ PAGE_SIZE << pool->p.order, pool->p.dma_dir);
+ set_page_private(page, 0);
+}
+
+/* Return a page to the page allocator, cleaning up our state */
+static void __page_pool_return_page(struct page_pool *pool, struct page *page)
+{
+ __page_pool_clean_page(pool, page);
+ put_page(page);
+ /* An optimization would be to call __free_pages(page, pool->p.order)
+ * knowing page is not part of page-cache (thus avoiding a
+ * __page_cache_release() call).
+ */
+}
+
+bool __page_pool_recycle_into_ring(struct page_pool *pool,
+ struct page *page)
+{
+ int ret;
+ /* BH protection not needed if current is serving softirq */
+ if (in_serving_softirq())
+ ret = ptr_ring_produce(&pool->ring, page);
+ else
+ ret = ptr_ring_produce_bh(&pool->ring, page);
+
+ return (ret == 0) ? true : false;
+}
+
+/* Only allow direct recycling in special circumstances, into the
+ * alloc side cache. E.g. during RX-NAPI processing for XDP_DROP use-case.
+ *
+ * Caller must provide appropriate safe context.
+ */
+static bool __page_pool_recycle_direct(struct page *page,
+ struct page_pool *pool)
+{
+ if (unlikely(pool->alloc.count == PP_ALLOC_CACHE_SIZE))
+ return false;
+
+ /* Caller MUST have verified/know (page_ref_count(page) == 1) */
+ pool->alloc.cache[pool->alloc.count++] = page;
+ return true;
+}
+
+void __page_pool_put_page(struct page_pool *pool,
+ struct page *page, bool allow_direct)
+{
+ /* This allocator is optimized for the XDP mode that uses
+ * one-frame-per-page, but have fallbacks that act like the
+ * regular page allocator APIs.
+ *
+ * refcnt == 1 means page_pool owns page, and can recycle it.
+ */
+ if (likely(page_ref_count(page) == 1)) {
+ /* Read barrier done in page_ref_count / READ_ONCE */
+
+ if (allow_direct && in_serving_softirq())
+ if (__page_pool_recycle_direct(page, pool))
+ return;
+
+ if (!__page_pool_recycle_into_ring(pool, page)) {
+ /* Cache full, fallback to free pages */
+ __page_pool_return_page(pool, page);
+ }
+ return;
+ }
+ /* Fallback/non-XDP mode: API user have elevated refcnt.
+ *
+ * Many drivers split up the page into fragments, and some
+ * want to keep doing this to save memory and do refcnt based
+ * recycling. Support this use case too, to ease drivers
+ * switching between XDP/non-XDP.
+ *
+ * In-case page_pool maintains the DMA mapping, API user must
+ * call page_pool_put_page once. In this elevated refcnt
+ * case, the DMA is unmapped/released, as driver is likely
+ * doing refcnt based recycle tricks, meaning another process
+ * will be invoking put_page.
+ */
+ __page_pool_clean_page(pool, page);
+ put_page(page);
+}
+EXPORT_SYMBOL(__page_pool_put_page);
+
+/* Cleanup and release resources */
+void __page_pool_destroy_rcu(struct rcu_head *rcu)
+{
+ struct page_pool *pool;
+ struct page *page;
+
+ pool = container_of(rcu, struct page_pool, rcu);
+
+ /* 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);
+ }
+
+ /* Empty recycle ring */
+ while ((page = ptr_ring_consume(&pool->ring))) {
+ /* Verify the refcnt invariant of cached pages */
+ if (!(page_ref_count(page) == 1)) {
+ pr_crit("%s() page_pool refcnt %d violation\n",
+ __func__, page_ref_count(page));
+ WARN_ON(1);
+ }
+ __page_pool_return_page(pool, page);
+ }
+ ptr_ring_cleanup(&pool->ring, NULL);
+ kfree(pool);
+}
+
+void page_pool_destroy_rcu(struct page_pool *pool)
+{
+ call_rcu(&pool->rcu, __page_pool_destroy_rcu);
+}
+EXPORT_SYMBOL(page_pool_destroy_rcu);
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 Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> --- include/net/page_pool.h | 133 +++++++++++++++++++ net/core/Makefile | 1 net/core/page_pool.c | 329 +++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 463 insertions(+) create mode 100644 include/net/page_pool.h create mode 100644 net/core/page_pool.c