Comment 3 for bug 1679126

Interesting, the culprit is:

commit cd958edb1fae85d0c7d1e1acbff82d22724e8d64
Author: Marc-André Lureau <email address hidden>
Date: Fri Aug 26 13:47:11 2016 +0400

    console: skip same-size resize

    virtio-gpu does a set-scanout at each frame (it might be a driver
    regression). qemu_console_resize() recreate a surface even if the size
    didn't change, and this shows up in profiling reports because the
    surface is cleared. With this patch, I get a +15-20% glmark2
    improvement.

    Signed-off-by: Marc-André Lureau <email address hidden>
    Message-id: <email address hidden>
    Signed-off-by: Gerd Hoffmann <email address hidden>

diff --git a/ui/console.c b/ui/console.c
index 3940762851..394786b3c7 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -2101,6 +2101,13 @@ void qemu_console_resize(QemuConsole *s, int width, int height)
     DisplaySurface *surface;

     assert(s->console_type == GRAPHIC_CONSOLE);
+
+ if (s->surface &&
+ pixman_image_get_width(s->surface->image) == width &&
+ pixman_image_get_height(s->surface->image) == height) {
+ return;
+ }