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>

1 files changed, 15 insertions, 12 deletions

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 6df29a62d72..3556268fe0a 100644
--- 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;