UPSTREAM: zram: reduce load operation in page_same_filled
In page_same_filled function, all elements in the page is compared with
next index value. The current comparison routine compares the (i)th and
(i+1)th values of the page.
In this case, two load operaions occur for each comparison. But if we
store first value of the page stores at 'val' variable and using it to
compare with others, the load opearation is reduced. It reduce load
operation per page by up to 64times.
Link: http://lkml.kernel.org/r/1488428104-7257-1-git-send-email-sangwoo2.park@lge.com
Signed-off-by: Sangwoo Park <sangwoo2.park@lge.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit f0fe9984656604ea8effd5ff82709ff8ce1f954b)
Signed-off-by: Peter Kalauskas <peskal@google.com>
Bug: 112488418
Change-Id: I007b6b8764749feeab1dd5123eb254e2c2265300
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 4d6d091..df55c2a 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -194,15 +194,17 @@
{
unsigned int pos;
unsigned long *page;
+ unsigned long val;
page = (unsigned long *)ptr;
+ val = page[0];
- for (pos = 0; pos < PAGE_SIZE / sizeof(*page) - 1; pos++) {
- if (page[pos] != page[pos + 1])
+ for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
+ if (val != page[pos])
return false;
}
- *element = page[pos];
+ *element = val;
return true;
}