zsmalloc: micro-optimize zs_object_copy()

A micro-optimization.  Avoid additional branching and reduce (a bit)
registry pressure (f.e.  s_off += size; d_off += size; may be calculated
twise: first for >= PAGE_SIZE check and later for offset update in "else"
clause).

scripts/bloat-o-meter shows some improvement

add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-10 (-10)
function                          old     new   delta
zs_object_copy                    550     540     -10

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 8705a01..a9a9ff2 100644 (file)
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1537,7 +1537,12 @@ static void zs_object_copy(unsigned long src, unsigned long dst,
                if (written == class->size)
                        break;
 
-               if (s_off + size >= PAGE_SIZE) {
+               s_off += size;
+               s_size -= size;
+               d_off += size;
+               d_size -= size;
+
+               if (s_off >= PAGE_SIZE) {
                        kunmap_atomic(d_addr);
                        kunmap_atomic(s_addr);
                        s_page = get_next_page(s_page);
@@ -1546,21 +1551,15 @@ static void zs_object_copy(unsigned long src, unsigned long dst,
                        d_addr = kmap_atomic(d_page);
                        s_size = class->size - written;
                        s_off = 0;
-               } else {
-                       s_off += size;
-                       s_size -= size;
                }
 
-               if (d_off + size >= PAGE_SIZE) {
+               if (d_off >= PAGE_SIZE) {
                        kunmap_atomic(d_addr);
                        d_page = get_next_page(d_page);
                        BUG_ON(!d_page);
                        d_addr = kmap_atomic(d_page);
                        d_size = class->size - written;
                        d_off = 0;
-               } else {
-                       d_off += size;
-                       d_size -= size;
                }
        }