xsk: Optimize for aligned case

Optimize for the aligned case by precomputing the parameter values of
the xdp_buff_xsk and xdp_buff structures in the heads array. We can do
this as the heads array size is equal to the number of chunks in the
umem for the aligned case. Then every entry in this array will reflect
a certain chunk/frame and can therefore be prepopulated with the
correct values and we can drop the use of the free_heads stack. Note
that it is not possible to allocate more buffers than what has been
allocated in the aligned case since each chunk can only contain a
single buffer.

We can unfortunately not do this in the unaligned case as one chunk
might contain multiple buffers. In this case, we keep the old scheme
of populating a heads entry every time it is used and using
the free_heads stack.

Also move xp_release() and xp_get_handle() to xsk_buff_pool.h. They
were for some reason in xsk.c even though they are buffer pool
operations.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210922075613.12186-7-magnus.karlsson@gmail.com

2 files changed, 34 insertions, 37 deletions

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index d6b500dc4208..f16074eb53c7 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -134,21 +134,6 @@ int xsk_reg_pool_at_qid(struct net_device *dev, struct xsk_buff_pool *pool,
 	return 0;
 }
 
-void xp_release(struct xdp_buff_xsk *xskb)
-{
-	xskb->pool->free_heads[xskb->pool->free_heads_cnt++] = xskb;
-}
-
-static u64 xp_get_handle(struct xdp_buff_xsk *xskb)
-{
-	u64 offset = xskb->xdp.data - xskb->xdp.data_hard_start;
-
-	offset += xskb->pool->headroom;
-	if (!xskb->pool->unaligned)
-		return xskb->orig_addr + offset;
-	return xskb->orig_addr + (offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT);
-}
-
 static int __xsk_rcv_zc(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
 {
 	struct xdp_buff_xsk *xskb = container_of(xdp, struct xdp_buff_xsk, xdp);
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 884d95d70f5e..96b14e51ba7e 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -44,12 +44,13 @@ void xp_destroy(struct xsk_buff_pool *pool)
 struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
 						struct xdp_umem *umem)
 {
+	bool unaligned = umem->flags & XDP_UMEM_UNALIGNED_CHUNK_FLAG;
 	struct xsk_buff_pool *pool;
 	struct xdp_buff_xsk *xskb;
-	u32 i;
+	u32 i, entries;
 
-	pool = kvzalloc(struct_size(pool, free_heads, umem->chunks),
-			GFP_KERNEL);
+	entries = unaligned ? umem->chunks : 0;
+	pool = kvzalloc(struct_size(pool, free_heads, entries),	GFP_KERNEL);
 	if (!pool)
 		goto out;
 
@@ -63,7 +64,8 @@ struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
 	pool->free_heads_cnt = umem->chunks;
 	pool->headroom = umem->headroom;
 	pool->chunk_size = umem->chunk_size;
-	pool->unaligned = umem->flags & XDP_UMEM_UNALIGNED_CHUNK_FLAG;
+	pool->chunk_shift = ffs(umem->chunk_size) - 1;
+	pool->unaligned = unaligned;
 	pool->frame_len = umem->chunk_size - umem->headroom -
 		XDP_PACKET_HEADROOM;
 	pool->umem = umem;
@@ -81,7 +83,10 @@ struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
 		xskb = &pool->heads[i];
 		xskb->pool = pool;
 		xskb->xdp.frame_sz = umem->chunk_size - umem->headroom;
-		pool->free_heads[i] = xskb;
+		if (pool->unaligned)
+			pool->free_heads[i] = xskb;
+		else
+			xp_init_xskb_addr(xskb, pool, i * pool->chunk_size);
 	}
 
 	return pool;
@@ -406,6 +411,12 @@ int xp_dma_map(struct xsk_buff_pool *pool, struct device *dev,
 
 	if (pool->unaligned)
 		xp_check_dma_contiguity(dma_map);
+	else
+		for (i = 0; i < pool->heads_cnt; i++) {
+			struct xdp_buff_xsk *xskb = &pool->heads[i];
+
+			xp_init_xskb_dma(xskb, pool, dma_map->dma_pages, xskb->orig_addr);
+		}
 
 	err = xp_init_dma_info(pool, dma_map);
 	if (err) {
@@ -448,8 +459,6 @@ static struct xdp_buff_xsk *__xp_alloc(struct xsk_buff_pool *pool)
 	if (pool->free_heads_cnt == 0)
 		return NULL;
 
-	xskb = pool->free_heads[--pool->free_heads_cnt];
-
 	for (;;) {
 		if (!xskq_cons_peek_addr_unchecked(pool->fq, &addr)) {
 			pool->fq->queue_empty_descs++;
@@ -466,17 +475,17 @@ static struct xdp_buff_xsk *__xp_alloc(struct xsk_buff_pool *pool)
 		}
 		break;
 	}
-	xskq_cons_release(pool->fq);
 
-	xskb->orig_addr = addr;
-	xskb->xdp.data_hard_start = pool->addrs + addr + pool->headroom;
-	if (pool->dma_pages_cnt) {
-		xskb->frame_dma = (pool->dma_pages[addr >> PAGE_SHIFT] &
-				   ~XSK_NEXT_PG_CONTIG_MASK) +
-				  (addr & ~PAGE_MASK);
-		xskb->dma = xskb->frame_dma + pool->headroom +
-			    XDP_PACKET_HEADROOM;
+	if (pool->unaligned) {
+		xskb = pool->free_heads[--pool->free_heads_cnt];
+		xp_init_xskb_addr(xskb, pool, addr);
+		if (pool->dma_pages_cnt)
+			xp_init_xskb_dma(xskb, pool, pool->dma_pages, addr);
+	} else {
+		xskb = &pool->heads[xp_aligned_extract_idx(pool, addr)];
 	}
+
+	xskq_cons_release(pool->fq);
 	return xskb;
 }
 
@@ -533,13 +542,16 @@ static u32 xp_alloc_new_from_fq(struct xsk_buff_pool *pool, struct xdp_buff **xd
 			continue;
 		}
 
-		xskb = pool->free_heads[--pool->free_heads_cnt];
+		if (pool->unaligned) {
+			xskb = pool->free_heads[--pool->free_heads_cnt];
+			xp_init_xskb_addr(xskb, pool, addr);
+			if (pool->dma_pages_cnt)
+				xp_init_xskb_dma(xskb, pool, pool->dma_pages, addr);
+		} else {
+			xskb = &pool->heads[xp_aligned_extract_idx(pool, addr)];
+		}
+
 		*xdp = &xskb->xdp;
-		xskb->orig_addr = addr;
-		xskb->xdp.data_hard_start = pool->addrs + addr + pool->headroom;
-		xskb->frame_dma = (pool->dma_pages[addr >> PAGE_SHIFT] &
-				   ~XSK_NEXT_PG_CONTIG_MASK) + (addr & ~PAGE_MASK);
-		xskb->dma = xskb->frame_dma + pool->headroom + XDP_PACKET_HEADROOM;
 		xdp++;
 	}