netdev - [PATCH net-next v2 06/10] netvsc: signal host if receive ring is emptied

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Date:   Wed, 26 Jul 2017 16:40:25 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        corbet@....net
Cc:     devel@...uxdriverproject.org, linux-doc@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH net-next v2 06/10] netvsc: signal host if receive ring is emptied

Latency improvement related to NAPI conversion.
If all packets are processed from receive ring then need
to signal host.

Signed-off-by: Stephen Hemminger <sthemmin@...rosoft.com>
---
 drivers/net/hyperv/netvsc.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 4c709b454d34..c5e6f7fc4f2b 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -1195,10 +1195,15 @@ int netvsc_poll(struct napi_struct *napi, int budget)
 		nvchan->desc = hv_pkt_iter_next(channel, nvchan->desc);
 	}
 
-	/* If send of  pending receive completions suceeded
-	 *   and did not exhaust NAPI budget
+	/* if ring is empty, signal host */
+	if (!nvchan->desc)
+		hv_pkt_iter_close(channel);
+
+	/* If send of pending receive completions suceeded
+	 *   and did not exhaust NAPI budget this time
 	 *   and not doing busy poll
-	 * then reschedule if more data has arrived from host
+	 * then re-enable host interrupts
+	 *     and reschedule if ring is not empty.
 	 */
 	if (send_recv_completions(nvchan) == 0 &&
 	    work_done < budget &&
-- 
2.11.0