svn commit: r341918 - stable/11/sys/dev/mlx4/mlx4_en

[Hans Petter Selasky]

Author: hselasky
Date: Wed Dec 12 11:57:27 2018
New Revision: 341918
URL: https://svnweb.freebsd.org/changeset/base/341918

Log:
  MFC r341552:
  mlx4en: Optimise reception of small packets.
  
  Copy small packets like TCP ACKs into a new mbuf
  reusing the existing mbuf to receive a new ethernet
  frame. This avoids wasting buffer space for
  small sized packets.
  
  Sponsored by:   Mellanox Technologies

Modified:
  stable/11/sys/dev/mlx4/mlx4_en/mlx4_en_rx.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/dev/mlx4/mlx4_en/mlx4_en_rx.c
==============================================================================
--- stable/11/sys/dev/mlx4/mlx4_en/mlx4_en_rx.c	Wed Dec 12 11:57:25 2018	(r341917)
+++ stable/11/sys/dev/mlx4/mlx4_en/mlx4_en_rx.c	Wed Dec 12 11:57:27 2018	(r341918)
@@ -629,6 +629,24 @@ mlx4_en_rx_mb(struct mlx4_en_priv *priv, struct mlx4_e
 #endif
 	struct mbuf *mb;
 
+	/* optimise reception of small packets */
+	if (length <= (MHLEN - MLX4_NET_IP_ALIGN) &&
+	    (mb = m_gethdr(M_NOWAIT, MT_DATA)) != NULL) {
+
+		/* set packet length */
+		mb->m_pkthdr.len = mb->m_len = length;
+
+		/* make sure IP header gets aligned */
+		mb->m_data += MLX4_NET_IP_ALIGN;
+
+		bus_dmamap_sync(ring->dma_tag, mb_list->dma_map,
+		    BUS_DMASYNC_POSTREAD);
+
+		bcopy(mtod(mb_list->mbuf, caddr_t), mtod(mb, caddr_t), length);
+
+		return (mb);
+	}
+
 	/* get mbuf */
 	mb = mb_list->mbuf;