netdev - [PATCH net-next v2 4/5] mvpp2: recycle buffers

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Date:   Fri,  2 Apr 2021 20:17:32 +0200
From:   Matteo Croce <mcroce@...ux.microsoft.com>
To:     netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Saeed Mahameed <saeedm@...dia.com>,
        David Ahern <dsahern@...il.com>,
        Saeed Mahameed <saeed@...nel.org>, Andrew Lunn <andrew@...n.ch>
Subject: [PATCH net-next v2 4/5] mvpp2: recycle buffers

From: Matteo Croce <mcroce@...rosoft.com>

Use the new recycling API for page_pool.
In a drop rate test, the packet rate is more than doubled,
from 962 Kpps to 2047 Kpps.

perf top on a stock system shows:

Overhead  Shared Object     Symbol
  30.67%  [kernel]          [k] page_pool_release_page
   8.37%  [kernel]          [k] get_page_from_freelist
   7.34%  [kernel]          [k] free_unref_page
   6.47%  [mvpp2]           [k] mvpp2_rx
   4.69%  [kernel]          [k] eth_type_trans
   4.55%  [kernel]          [k] __netif_receive_skb_core
   4.40%  [kernel]          [k] build_skb
   4.29%  [kernel]          [k] kmem_cache_free
   4.00%  [kernel]          [k] kmem_cache_alloc
   3.81%  [kernel]          [k] dev_gro_receive

With packet rate stable at 962 Kpps:

tx: 0 bps 0 pps rx: 477.4 Mbps 962.6 Kpps
tx: 0 bps 0 pps rx: 477.6 Mbps 962.8 Kpps
tx: 0 bps 0 pps rx: 477.6 Mbps 962.9 Kpps
tx: 0 bps 0 pps rx: 477.2 Mbps 962.1 Kpps
tx: 0 bps 0 pps rx: 477.5 Mbps 962.7 Kpps

And this is the same output with recycling enabled:

Overhead  Shared Object     Symbol
  12.75%  [mvpp2]           [k] mvpp2_rx
   9.56%  [kernel]          [k] __netif_receive_skb_core
   9.29%  [kernel]          [k] build_skb
   9.27%  [kernel]          [k] eth_type_trans
   8.39%  [kernel]          [k] kmem_cache_alloc
   7.85%  [kernel]          [k] kmem_cache_free
   7.36%  [kernel]          [k] page_pool_put_page
   6.45%  [kernel]          [k] dev_gro_receive
   4.72%  [kernel]          [k] __xdp_return
   3.06%  [kernel]          [k] page_pool_refill_alloc_cache

With packet rate above 2000 Kpps:

tx: 0 bps 0 pps rx: 1015 Mbps 2046 Kpps
tx: 0 bps 0 pps rx: 1015 Mbps 2047 Kpps
tx: 0 bps 0 pps rx: 1015 Mbps 2047 Kpps
tx: 0 bps 0 pps rx: 1015 Mbps 2047 Kpps
tx: 0 bps 0 pps rx: 1015 Mbps 2047 Kpps

The major performance increase is explained by the fact that the most CPU
consuming functions (page_pool_release_page, get_page_from_freelist
and free_unref_page) are no longer called on a per packet basis.

The test was done by sending to the macchiatobin 64 byte ethernet frames
with an invalid ethertype, so the packets are dropped early in the RX path.

Signed-off-by: Matteo Croce <mcroce@...rosoft.com>
---
 drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
index ec706d614cac..633b39cfef65 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -3847,6 +3847,7 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
 	struct mvpp2_pcpu_stats ps = {};
 	enum dma_data_direction dma_dir;
 	struct bpf_prog *xdp_prog;
+	struct xdp_rxq_info *rxqi;
 	struct xdp_buff xdp;
 	int rx_received;
 	int rx_done = 0;
@@ -3912,15 +3913,15 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
 		else
 			frag_size = bm_pool->frag_size;
 
-		if (xdp_prog) {
-			struct xdp_rxq_info *xdp_rxq;
+		if (bm_pool->pkt_size == MVPP2_BM_SHORT_PKT_SIZE)
+			rxqi = &rxq->xdp_rxq_short;
+		else
+			rxqi = &rxq->xdp_rxq_long;
 
-			if (bm_pool->pkt_size == MVPP2_BM_SHORT_PKT_SIZE)
-				xdp_rxq = &rxq->xdp_rxq_short;
-			else
-				xdp_rxq = &rxq->xdp_rxq_long;
+		if (xdp_prog) {
+			xdp.rxq = rxqi;
 
-			xdp_init_buff(&xdp, PAGE_SIZE, xdp_rxq);
+			xdp_init_buff(&xdp, PAGE_SIZE, rxqi);
 			xdp_prepare_buff(&xdp, data,
 					 MVPP2_MH_SIZE + MVPP2_SKB_HEADROOM,
 					 rx_bytes, false);
@@ -3964,7 +3965,7 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
 		}
 
 		if (pp)
-			page_pool_release_page(pp, virt_to_page(data));
+			skb_mark_for_recycle(skb, virt_to_page(data), &rxqi->mem);
 		else
 			dma_unmap_single_attrs(dev->dev.parent, dma_addr,
 					       bm_pool->buf_size, DMA_FROM_DEVICE,
-- 
2.30.2