svn commit: r297809 - head/sys/dev/hyperv/netvsc

[Sepherosa Ziehau]

Author: sephe
Date: Mon Apr 11 06:31:52 2016
New Revision: 297809
URL: https://svnweb.freebsd.org/changeset/base/297809

Log:
  hyperv/hn: Cap default # of rings to 8.
  
  8 gives the best performance in both Azure and local Hyper-V on both
  10Ge and 40Ge. More rings are still allowed by manual configuration.
  
  Reviewed by:	Dexuan Cui <decui microsoft com>
  MFC after:	1 week
  Sponsored by:	Microsoft OSTC
  Differential Revision:	https://reviews.freebsd.org/D5879

Modified:
  head/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c

Modified: head/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
==============================================================================
--- head/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c	Mon Apr 11 06:22:26 2016	(r297808)
+++ head/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c	Mon Apr 11 06:31:52 2016	(r297809)
@@ -136,6 +136,8 @@ __FBSDID("$FreeBSD$");
 
 #define HN_LROENT_CNT_DEF		128
 
+#define HN_RING_CNT_DEF_MAX		8
+
 #define HN_RNDIS_MSG_LEN		\
     (sizeof(rndis_msg) +		\
      RNDIS_HASH_PPI_SIZE +		\
@@ -460,8 +462,14 @@ netvsc_attach(device_t dev)
 	 * The # of RX rings to use is same as the # of channels to use.
 	 */
 	ring_cnt = hn_chan_cnt;
-	if (ring_cnt <= 0 || ring_cnt > mp_ncpus)
+	if (ring_cnt <= 0) {
+		/* Default */
+		ring_cnt = mp_ncpus;
+		if (ring_cnt > HN_RING_CNT_DEF_MAX)
+			ring_cnt = HN_RING_CNT_DEF_MAX;
+	} else if (ring_cnt > mp_ncpus) {
 		ring_cnt = mp_ncpus;
+	}
 
 	tx_ring_cnt = hn_tx_ring_cnt;
 	if (tx_ring_cnt <= 0 || tx_ring_cnt > ring_cnt)