[Qemu-devel] [6862] vnc: throttle screen updates.

[Anthony Liguori]

Revision: 6862
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=6862
Author:   aliguori
Date:     2009-03-20 15:59:24 +0000 (Fri, 20 Mar 2009)
Log Message:
-----------
vnc: throttle screen updates. (Gerd Hoffmann)

This patch makes the vnc server code skip screen refreshes in case
there is data in the output buffer.  This reduces the refresh rate to
throttle the bandwidth needed in case the network link is saturated.

Signed-off-by: Gerd Hoffmann <address@hidden>
Signed-off-by: Anthony Liguori <address@hidden>

Modified Paths:
--------------
    trunk/vnc.c
    trunk/vnc.h

Modified: trunk/vnc.c
===================================================================
--- trunk/vnc.c 2009-03-20 15:59:18 UTC (rev 6861)
+++ trunk/vnc.c 2009-03-20 15:59:24 UTC (rev 6862)
@@ -657,6 +657,7 @@
 
 static void vnc_copy(VncState *vs, int src_x, int src_y, int dst_x, int dst_y, 
int w, int h)
 {
+    vs->force_update = 1;
     vnc_update_client(vs);
 
     vnc_write_u8(vs, 0);  /* msg id */
@@ -710,6 +711,12 @@
         int saved_offset;
         int has_dirty = 0;
 
+        if (vs->output.offset && !vs->audio_cap && !vs->force_update) {
+            /* kernel send buffers are full -> drop frames to throttle */
+            qemu_mod_timer(vs->timer, qemu_get_clock(rt_clock) + 
VNC_REFRESH_INTERVAL);
+            return;
+        }
+
         vga_hw_update();
 
         /*
@@ -745,7 +752,7 @@
             server_row += ds_get_linesize(vs->ds);
         }
 
-        if (!has_dirty && !vs->audio_cap) {
+        if (!has_dirty && !vs->audio_cap && !vs->force_update) {
             qemu_mod_timer(vs->timer, qemu_get_clock(rt_clock) + 
VNC_REFRESH_INTERVAL);
             return;
         }
@@ -789,6 +796,7 @@
         vs->output.buffer[saved_offset] = (n_rectangles >> 8) & 0xFF;
         vs->output.buffer[saved_offset + 1] = n_rectangles & 0xFF;
         vnc_flush(vs);
+        vs->force_update = 0;
 
     }
 
@@ -1407,6 +1415,7 @@
 
     int i;
     vs->need_update = 1;
+    vs->force_update = 1;
     if (!incremental) {
         for (i = 0; i < h; i++) {
             vnc_set_bits(vs->guest.dirty[y_position + i],

Modified: trunk/vnc.h
===================================================================
--- trunk/vnc.h 2009-03-20 15:59:18 UTC (rev 6861)
+++ trunk/vnc.h 2009-03-20 15:59:24 UTC (rev 6862)
@@ -121,6 +121,7 @@
 
     VncDisplay *vd;
     int need_update;
+    int force_update;
     uint32_t features;
     int absolute;
     int last_x;