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ui/vnc: optimize clearing in find_and_clear_dirty_height()

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The following artifical test (just the bitmap operation part) running
vnc_update_client 65536 times on a 2560x2048 surface illustrates the
performance difference:

All bits clean - vnc_update_client_new: 0.07 secs
                 vnc_update_client_new2: 0.07 secs
                 vnc_update_client_old: 10.98 secs

All bits dirty - vnc_update_client_new: 11.26 secs
               - vnc_update_client_new2: 0.29 secs
                 vnc_update_client_old: 20.19 secs

Few bits dirty - vnc_update_client_new: 0.07 secs
               - vnc_update_client_new2: 0.07 secs
                 vnc_update_client_old: 10.98 secs

vnc_update_client_new2 shows the performance of vnc_update_client
with this patch added.

Comparing with the test run of the last patch the performance
is at least unchanged while it is significantly improved
for the all bits dirty case.

Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Peter Lieven 2014-01-08 10:08:36 +01:00 committed by Gerd Hoffmann
parent 12b316d4c1
commit 863d7c9105
1 changed files with 1 additions and 4 deletions
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5
ui/vnc.c
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@ -879,13 +879,10 @@ static int find_and_clear_dirty_height(struct VncState *vs,
int h;
for (h = 1; h < (height - y); h++) {
int tmp_x;
if (!test_bit(last_x, vs->dirty[y + h])) {
break;
}
for (tmp_x = last_x; tmp_x < x; tmp_x++) {
clear_bit(tmp_x, vs->dirty[y + h]);
}
bitmap_clear(vs->dirty[y + h], last_x, x - last_x);
}
return h;