Merge branch 'remove-page-frag-implementation-in-vhost_net'

Yunsheng Lin says:

====================
remove page frag implementation in vhost_net

Currently there are three implementations for page frag:

1. mm/page_alloc.c: net stack seems to be using it in the
   rx part with 'struct page_frag_cache' and the main API
   being page_frag_alloc_align().
2. net/core/sock.c: net stack seems to be using it in the
   tx part with 'struct page_frag' and the main API being
   skb_page_frag_refill().
3. drivers/vhost/net.c: vhost seems to be using it to build
   xdp frame, and it's implementation seems to be a mix of
   the above two.

This patchset tries to unfiy the page frag implementation a
little bit by unifying gfp bit for order 3 page allocation
and replacing page frag implementation in vhost.c with the
one in page_alloc.c.

After this patchset, we are not only able to unify the page
frag implementation a little, but also able to have about
0.5% performance boost testing by using the vhost_net_test
introduced in the last patch.

Before this patchset:
Performance counter stats for './vhost_net_test' (10 runs):

     305325.78 msec task-clock                       #    1.738 CPUs utilized               ( +-  0.12% )
       1048668      context-switches                 #    3.435 K/sec                       ( +-  0.00% )
            11      cpu-migrations                   #    0.036 /sec                        ( +- 17.64% )
            33      page-faults                      #    0.108 /sec                        ( +-  0.49% )
  244651819491      cycles                           #    0.801 GHz                         ( +-  0.43% )  (64)
   64714638024      stalled-cycles-frontend          #   26.45% frontend cycles idle        ( +-  2.19% )  (67)
   30774313491      stalled-cycles-backend           #   12.58% backend cycles idle         ( +-  7.68% )  (70)
  201749748680      instructions                     #    0.82  insn per cycle
                                              #    0.32  stalled cycles per insn     ( +-  0.41% )  (66.76%)
   65494787909      branches                         #  214.508 M/sec                       ( +-  0.35% )  (64)
    4284111313      branch-misses                    #    6.54% of all branches             ( +-  0.45% )  (66)

       175.699 +- 0.189 seconds time elapsed  ( +-  0.11% )

After this patchset:
Performance counter stats for './vhost_net_test' (10 runs):

     303974.38 msec task-clock                       #    1.739 CPUs utilized               ( +-  0.14% )
       1048807      context-switches                 #    3.450 K/sec                       ( +-  0.00% )
            14      cpu-migrations                   #    0.046 /sec                        ( +- 12.86% )
            33      page-faults                      #    0.109 /sec                        ( +-  0.46% )
  251289376347      cycles                           #    0.827 GHz                         ( +-  0.32% )  (60)
   67885175415      stalled-cycles-frontend          #   27.01% frontend cycles idle        ( +-  0.48% )  (63)
   27809282600      stalled-cycles-backend           #   11.07% backend cycles idle         ( +-  0.36% )  (71)
  195543234672      instructions                     #    0.78  insn per cycle
                                              #    0.35  stalled cycles per insn     ( +-  0.29% )  (69.04%)
   62423183552      branches                         #  205.357 M/sec                       ( +-  0.48% )  (67)
    4135666632      branch-misses                    #    6.63% of all branches             ( +-  0.63% )  (67)

       174.764 +- 0.214 seconds time elapsed  ( +-  0.12% )

Changelog:
V6: Add timeout for poll() and simplify some logic as suggested
    by Jason.

V5: Address the comment from jason in vhost_net_test.c and the
    comment about leaving out the gfp change for page frag in
    sock.c as suggested by Paolo.

V4: Resend based on latest net-next branch.

V3:
1. Add __page_frag_alloc_align() which is passed with the align mask
   the original function expected as suggested by Alexander.
2. Drop patch 3 in v2 suggested by Alexander.
3. Reorder patch 4 & 5 in v2 suggested by Alexander.

Note that placing this gfp flags handing for order 3 page in an inline
function is not considered, as we may be able to unify the page_frag
and page_frag_cache handling.

V2: Change 'xor'd' to 'masked off', add vhost tx testing for
    vhost_net_test.

V1: Fix some typo, drop RFC tag and rebase on latest net-next.
====================

Link: https://lore.kernel.org/r/20240228093013.8263-1-linyunsheng@huawei.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/google/gve/gve_main.c

@@ -1276,17 +1276,10 @@ static void gve_unreg_xdp_info(struct gve_priv *priv)
 
 static void gve_drain_page_cache(struct gve_priv *priv)
 {
-	struct page_frag_cache *nc;
 	int i;
 
-	for (i = 0; i < priv->rx_cfg.num_queues; i++) {
-		nc = &priv->rx[i].page_cache;
-		if (nc->va) {
-			__page_frag_cache_drain(virt_to_page(nc->va),
-						nc->pagecnt_bias);
-			nc->va = NULL;
-		}
-	}
+	for (i = 0; i < priv->rx_cfg.num_queues; i++)
+		page_frag_cache_drain(&priv->rx[i].page_cache);
 }
 
 static void gve_qpls_get_curr_alloc_cfg(struct gve_priv *priv,

drivers/net/ethernet/mediatek/mtk_wed_wo.c

@@ -286,7 +286,6 @@ mtk_wed_wo_queue_free(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
 static void
 mtk_wed_wo_queue_tx_clean(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
 {
-	struct page *page;
 	int i;
 
 	for (i = 0; i < q->n_desc; i++) {
@@ -301,19 +300,12 @@ mtk_wed_wo_queue_tx_clean(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
 		entry->buf = NULL;
 	}
 
-	if (!q->cache.va)
-		return;
-
-	page = virt_to_page(q->cache.va);
-	__page_frag_cache_drain(page, q->cache.pagecnt_bias);
-	memset(&q->cache, 0, sizeof(q->cache));
+	page_frag_cache_drain(&q->cache);
 }
 
 static void
 mtk_wed_wo_queue_rx_clean(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
 {
-	struct page *page;
-
 	for (;;) {
 		void *buf = mtk_wed_wo_dequeue(wo, q, NULL, true);
 
@@ -323,12 +315,7 @@ mtk_wed_wo_queue_rx_clean(struct mtk_wed_wo *wo, struct mtk_wed_wo_queue *q)
 		skb_free_frag(buf);
 	}
 
-	if (!q->cache.va)
-		return;
-
-	page = virt_to_page(q->cache.va);
-	__page_frag_cache_drain(page, q->cache.pagecnt_bias);
-	memset(&q->cache, 0, sizeof(q->cache));
+	page_frag_cache_drain(&q->cache);
 }
 
 static void

drivers/nvme/host/tcp.c

@@ -1344,7 +1344,6 @@ static int nvme_tcp_alloc_async_req(struct nvme_tcp_ctrl *ctrl)
 
 static void nvme_tcp_free_queue(struct nvme_ctrl *nctrl, int qid)
 {
-	struct page *page;
 	struct nvme_tcp_ctrl *ctrl = to_tcp_ctrl(nctrl);
 	struct nvme_tcp_queue *queue = &ctrl->queues[qid];
 	unsigned int noreclaim_flag;
@@ -1355,11 +1354,7 @@ static void nvme_tcp_free_queue(struct nvme_ctrl *nctrl, int qid)
 	if (queue->hdr_digest || queue->data_digest)
 		nvme_tcp_free_crypto(queue);
 
-	if (queue->pf_cache.va) {
-		page = virt_to_head_page(queue->pf_cache.va);
-		__page_frag_cache_drain(page, queue->pf_cache.pagecnt_bias);
-		queue->pf_cache.va = NULL;
-	}
+	page_frag_cache_drain(&queue->pf_cache);
 
 	noreclaim_flag = memalloc_noreclaim_save();
 	/* ->sock will be released by fput() */

drivers/nvme/target/tcp.c

@@ -1591,7 +1591,6 @@ static void nvmet_tcp_free_cmd_data_in_buffers(struct nvmet_tcp_queue *queue)
 
 static void nvmet_tcp_release_queue_work(struct work_struct *w)
 {
-	struct page *page;
 	struct nvmet_tcp_queue *queue =
 		container_of(w, struct nvmet_tcp_queue, release_work);
 
@@ -1615,8 +1614,7 @@ static void nvmet_tcp_release_queue_work(struct work_struct *w)
 	if (queue->hdr_digest || queue->data_digest)
 		nvmet_tcp_free_crypto(queue);
 	ida_free(&nvmet_tcp_queue_ida, queue->idx);
-	page = virt_to_head_page(queue->pf_cache.va);
-	__page_frag_cache_drain(page, queue->pf_cache.pagecnt_bias);
+	page_frag_cache_drain(&queue->pf_cache);
 	kfree(queue);
 }
 

drivers/vhost/net.c

@@ -141,10 +141,8 @@ struct vhost_net {
 	unsigned tx_zcopy_err;
 	/* Flush in progress. Protected by tx vq lock. */
 	bool tx_flush;
-	/* Private page frag */
-	struct page_frag page_frag;
-	/* Refcount bias of page frag */
-	int refcnt_bias;
+	/* Private page frag cache */
+	struct page_frag_cache pf_cache;
 };
 
 static unsigned vhost_net_zcopy_mask __read_mostly;
@@ -655,41 +653,6 @@ static bool tx_can_batch(struct vhost_virtqueue *vq, size_t total_len)
 	       !vhost_vq_avail_empty(vq->dev, vq);
 }
 
-static bool vhost_net_page_frag_refill(struct vhost_net *net, unsigned int sz,
-				       struct page_frag *pfrag, gfp_t gfp)
-{
-	if (pfrag->page) {
-		if (pfrag->offset + sz <= pfrag->size)
-			return true;
-		__page_frag_cache_drain(pfrag->page, net->refcnt_bias);
-	}
-
-	pfrag->offset = 0;
-	net->refcnt_bias = 0;
-	if (SKB_FRAG_PAGE_ORDER) {
-		/* Avoid direct reclaim but allow kswapd to wake */
-		pfrag->page = alloc_pages((gfp & ~__GFP_DIRECT_RECLAIM) |
-					  __GFP_COMP | __GFP_NOWARN |
-					  __GFP_NORETRY,
-					  SKB_FRAG_PAGE_ORDER);
-		if (likely(pfrag->page)) {
-			pfrag->size = PAGE_SIZE << SKB_FRAG_PAGE_ORDER;
-			goto done;
-		}
-	}
-	pfrag->page = alloc_page(gfp);
-	if (likely(pfrag->page)) {
-		pfrag->size = PAGE_SIZE;
-		goto done;
-	}
-	return false;
-
-done:
-	net->refcnt_bias = USHRT_MAX;
-	page_ref_add(pfrag->page, USHRT_MAX - 1);
-	return true;
-}
-
 #define VHOST_NET_RX_PAD (NET_IP_ALIGN + NET_SKB_PAD)
 
 static int vhost_net_build_xdp(struct vhost_net_virtqueue *nvq,
@@ -699,7 +662,6 @@ static int vhost_net_build_xdp(struct vhost_net_virtqueue *nvq,
 	struct vhost_net *net = container_of(vq->dev, struct vhost_net,
 					     dev);
 	struct socket *sock = vhost_vq_get_backend(vq);
-	struct page_frag *alloc_frag = &net->page_frag;
 	struct virtio_net_hdr *gso;
 	struct xdp_buff *xdp = &nvq->xdp[nvq->batched_xdp];
 	struct tun_xdp_hdr *hdr;
@@ -710,6 +672,7 @@ static int vhost_net_build_xdp(struct vhost_net_virtqueue *nvq,
 	int sock_hlen = nvq->sock_hlen;
 	void *buf;
 	int copied;
+	int ret;
 
 	if (unlikely(len < nvq->sock_hlen))
 		return -EFAULT;
@@ -719,18 +682,17 @@ static int vhost_net_build_xdp(struct vhost_net_virtqueue *nvq,
 		return -ENOSPC;
 
 	buflen += SKB_DATA_ALIGN(len + pad);
-	alloc_frag->offset = ALIGN((u64)alloc_frag->offset, SMP_CACHE_BYTES);
-	if (unlikely(!vhost_net_page_frag_refill(net, buflen,
-						 alloc_frag, GFP_KERNEL)))
+	buf = page_frag_alloc_align(&net->pf_cache, buflen, GFP_KERNEL,
+				    SMP_CACHE_BYTES);
+	if (unlikely(!buf))
 		return -ENOMEM;
 
-	buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
-	copied = copy_page_from_iter(alloc_frag->page,
-				     alloc_frag->offset +
-				     offsetof(struct tun_xdp_hdr, gso),
+	copied = copy_from_iter(buf + offsetof(struct tun_xdp_hdr, gso),
 				sock_hlen, from);
-	if (copied != sock_hlen)
-		return -EFAULT;
+	if (copied != sock_hlen) {
+		ret = -EFAULT;
+		goto err;
+	}
 
 	hdr = buf;
 	gso = &hdr->gso;
@@ -743,27 +705,30 @@ static int vhost_net_build_xdp(struct vhost_net_virtqueue *nvq,
 			       vhost16_to_cpu(vq, gso->csum_start) +
 			       vhost16_to_cpu(vq, gso->csum_offset) + 2);
 
-		if (vhost16_to_cpu(vq, gso->hdr_len) > len)
-			return -EINVAL;
+		if (vhost16_to_cpu(vq, gso->hdr_len) > len) {
+			ret = -EINVAL;
+			goto err;
+		}
 	}
 
 	len -= sock_hlen;
-	copied = copy_page_from_iter(alloc_frag->page,
-				     alloc_frag->offset + pad,
-				     len, from);
-	if (copied != len)
-		return -EFAULT;
+	copied = copy_from_iter(buf + pad, len, from);
+	if (copied != len) {
+		ret = -EFAULT;
+		goto err;
+	}
 
 	xdp_init_buff(xdp, buflen, NULL);
 	xdp_prepare_buff(xdp, buf, pad, len, true);
 	hdr->buflen = buflen;
 
-	--net->refcnt_bias;
-	alloc_frag->offset += buflen;
-
 	++nvq->batched_xdp;
 
 	return 0;
+
+err:
+	page_frag_free(buf);
+	return ret;
 }
 
 static void handle_tx_copy(struct vhost_net *net, struct socket *sock)
@@ -1353,8 +1318,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
 			vqs[VHOST_NET_VQ_RX]);
 
 	f->private_data = n;
-	n->page_frag.page = NULL;
-	n->refcnt_bias = 0;
+	n->pf_cache.va = NULL;
 
 	return 0;
 }
@@ -1422,8 +1386,7 @@ static int vhost_net_release(struct inode *inode, struct file *f)
 	kfree(n->vqs[VHOST_NET_VQ_RX].rxq.queue);
 	kfree(n->vqs[VHOST_NET_VQ_TX].xdp);
 	kfree(n->dev.vqs);
-	if (n->page_frag.page)
-		__page_frag_cache_drain(n->page_frag.page, n->refcnt_bias);
+	page_frag_cache_drain(&n->pf_cache);
 	kvfree(n);
 	return 0;
 }

include/linux/gfp.h

@@ -311,15 +311,23 @@ extern void __free_pages(struct page *page, unsigned int order);
 extern void free_pages(unsigned long addr, unsigned int order);
 
 struct page_frag_cache;
+void page_frag_cache_drain(struct page_frag_cache *nc);
 extern void __page_frag_cache_drain(struct page *page, unsigned int count);
-extern void *page_frag_alloc_align(struct page_frag_cache *nc,
+void *__page_frag_alloc_align(struct page_frag_cache *nc, unsigned int fragsz,
+			      gfp_t gfp_mask, unsigned int align_mask);
+
+static inline void *page_frag_alloc_align(struct page_frag_cache *nc,
 					  unsigned int fragsz, gfp_t gfp_mask,
-				   unsigned int align_mask);
+					  unsigned int align)
+{
+	WARN_ON_ONCE(!is_power_of_2(align));
+	return __page_frag_alloc_align(nc, fragsz, gfp_mask, -align);
+}
 
 static inline void *page_frag_alloc(struct page_frag_cache *nc,
 			     unsigned int fragsz, gfp_t gfp_mask)
 {
-	return page_frag_alloc_align(nc, fragsz, gfp_mask, ~0u);
+	return __page_frag_alloc_align(nc, fragsz, gfp_mask, ~0u);
 }
 
 extern void page_frag_free(void *addr);

mm/page_alloc.c

@@ -4685,8 +4685,8 @@ static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
 	gfp_t gfp = gfp_mask;
 
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
-	gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
-		    __GFP_NOMEMALLOC;
+	gfp_mask = (gfp_mask & ~__GFP_DIRECT_RECLAIM) |  __GFP_COMP |
+		   __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC;
 	page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
 				PAGE_FRAG_CACHE_MAX_ORDER);
 	nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE;
@@ -4699,6 +4699,16 @@ static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
 	return page;
 }
 
+void page_frag_cache_drain(struct page_frag_cache *nc)
+{
+	if (!nc->va)
+		return;
+
+	__page_frag_cache_drain(virt_to_head_page(nc->va), nc->pagecnt_bias);
+	nc->va = NULL;
+}
+EXPORT_SYMBOL(page_frag_cache_drain);
+
 void __page_frag_cache_drain(struct page *page, unsigned int count)
 {
 	VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
@@ -4708,7 +4718,7 @@ void __page_frag_cache_drain(struct page *page, unsigned int count)
 }
 EXPORT_SYMBOL(__page_frag_cache_drain);
 
-void *page_frag_alloc_align(struct page_frag_cache *nc,
+void *__page_frag_alloc_align(struct page_frag_cache *nc,
 			      unsigned int fragsz, gfp_t gfp_mask,
 			      unsigned int align_mask)
 {
@@ -4779,7 +4789,7 @@ void *page_frag_alloc_align(struct page_frag_cache *nc,
 
 	return nc->va + offset;
 }
-EXPORT_SYMBOL(page_frag_alloc_align);
+EXPORT_SYMBOL(__page_frag_alloc_align);
 
 /*
  * Frees a page fragment allocated out of either a compound or order 0 page.

net/core/skbuff.c

@@ -315,7 +315,8 @@ void *__napi_alloc_frag_align(unsigned int fragsz, unsigned int align_mask)
 
 	fragsz = SKB_DATA_ALIGN(fragsz);
 
-	return page_frag_alloc_align(&nc->page, fragsz, GFP_ATOMIC, align_mask);
+	return __page_frag_alloc_align(&nc->page, fragsz, GFP_ATOMIC,
+				       align_mask);
 }
 EXPORT_SYMBOL(__napi_alloc_frag_align);
 
@@ -327,13 +328,15 @@ void *__netdev_alloc_frag_align(unsigned int fragsz, unsigned int align_mask)
 	if (in_hardirq() || irqs_disabled()) {
 		struct page_frag_cache *nc = this_cpu_ptr(&netdev_alloc_cache);
 
-		data = page_frag_alloc_align(nc, fragsz, GFP_ATOMIC, align_mask);
+		data = __page_frag_alloc_align(nc, fragsz, GFP_ATOMIC,
+					       align_mask);
 	} else {
 		struct napi_alloc_cache *nc;
 
 		local_bh_disable();
 		nc = this_cpu_ptr(&napi_alloc_cache);
-		data = page_frag_alloc_align(&nc->page, fragsz, GFP_ATOMIC, align_mask);
+		data = __page_frag_alloc_align(&nc->page, fragsz, GFP_ATOMIC,
+					       align_mask);
 		local_bh_enable();
 	}
 	return data;

tools/virtio/.gitignore

 # SPDX-License-Identifier: GPL-2.0-only
 *.d
 virtio_test
+vhost_net_test
 vringh_test
 virtio-trace/trace-agent

tools/virtio/Makefile

 # SPDX-License-Identifier: GPL-2.0
 all: test mod
-test: virtio_test vringh_test
+test: virtio_test vringh_test vhost_net_test
 virtio_test: virtio_ring.o virtio_test.o
 vringh_test: vringh_test.o vringh.o virtio_ring.o
+vhost_net_test: virtio_ring.o vhost_net_test.o
 
 try-run = $(shell set -e;		\
 	if ($(1)) >/dev/null 2>&1;	\
@@ -49,6 +50,7 @@ oot-clean: OOT_BUILD+=clean
 
 .PHONY: all test mod clean vhost oot oot-clean oot-build
 clean:
-	${RM} *.o vringh_test virtio_test vhost_test/*.o vhost_test/.*.cmd \
-              vhost_test/Module.symvers vhost_test/modules.order *.d
+	${RM} *.o vringh_test virtio_test vhost_net_test vhost_test/*.o \
+              vhost_test/.*.cmd vhost_test/Module.symvers \
+              vhost_test/modules.order *.d
 -include *.d

tools/virtio/linux/virtio_config.h

 /* SPDX-License-Identifier: GPL-2.0 */
+#ifndef LINUX_VIRTIO_CONFIG_H
+#define LINUX_VIRTIO_CONFIG_H
 #include <linux/virtio_byteorder.h>
 #include <linux/virtio.h>
 #include <uapi/linux/virtio_config.h>
@@ -95,3 +97,5 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
 {
 	return __cpu_to_virtio64(virtio_is_little_endian(vdev), val);
 }
+
+#endif