From: Paul Durrant <paul.durrant@citrix.com>
Date: Wed, 18 May 2016 15:33:14 +0000 (+0100)
Subject: Defer transmit response event until the last possible moment
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=66da96ba16105371e3ac8cb0d781ec01c53a0876;p=people%2Fpauldu%2Fxenvif.git

Defer transmit response event until the last possible moment

When sending packets, there is no need to enable a transmit reponse
event until the ring fills or there are no more packets to send.

This patch therefore defers advancing the ring event count until just
before a batch of packets are pushed.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
---

diff --git a/src/xenvif/transmitter.c b/src/xenvif/transmitter.c
index 95c3479..b55daa3 100644
--- a/src/xenvif/transmitter.c
+++ b/src/xenvif/transmitter.c
@@ -2604,7 +2604,6 @@ TransmitterRingPoll(
         KeMemoryBarrier();
 
         Ring->Front.rsp_cons = rsp_cons;
-        Ring->Shared->rsp_event = rsp_cons + 1;
     }
 
 done:
@@ -2678,6 +2677,8 @@ __TransmitterRingPushRequests(
 #pragma warning (push)
 #pragma warning (disable:4244)
 
+    Ring->Shared->rsp_event = Ring->Front.req_prod_pvt;
+
     // Make the requests visible to the backend
     RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&Ring->Front, Notify);