vgacon: optimize scrolling

Join multiple scr_memcpyw into 1-3 calls (usually 2).  (benchmarked
average speedup: 1%)

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Cc: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 6df29a62d7202552d63ced7bfc588ef8854d6c49..3556268fe0a0ad8482d7250a7cdc5f867f0a74ac 100644 (file)
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -292,23 +292,26 @@ static int vgacon_scrolldelta(struct vc_data *c, int lines)
        d = (void *) c->vc_origin;
        s = (void *) c->vc_screenbuf;
 
-       while (count--) {
-               scr_memcpyw(d, vgacon_scrollback + soff, c->vc_size_row);
-               d += c->vc_size_row;
-               soff += c->vc_size_row;
-
-               if (soff >= vgacon_scrollback_size)
-                       soff = 0;
+       if (count) {
+               int copysize;
+               count *= c->vc_size_row;
+               /* how much memory to end of buffer left? */
+               copysize = min(count, vgacon_scrollback_size - soff);
+               scr_memcpyw(d, vgacon_scrollback + soff, copysize);
+               d += copysize;
+               count -= copysize;
+
+               if (count) {
+                       scr_memcpyw(d, vgacon_scrollback, count);
+                       d += count;
+               }
        }
 
        if (diff == c->vc_rows) {
                vgacon_cursor(c, CM_MOVE);
        } else {
-               while (diff--) {
-                       scr_memcpyw(d, s, c->vc_size_row);
-                       d += c->vc_size_row;
-                       s += c->vc_size_row;
-               }
+               if (diff)
+                       scr_memcpyw(d, s, diff * c->vc_size_row);
        }
 
        return 1;