From 3369bb2093c6cb72d29ee554a7ce0be22d026d8c Mon Sep 17 00:00:00 2001 From: Sangwoo Park Date: Wed, 3 May 2017 14:55:56 -0700 Subject: [PATCH] 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 Reviewed-by: Sergey Senozhatsky Acked-by: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds (cherry picked from commit f0fe9984656604ea8effd5ff82709ff8ce1f954b) Signed-off-by: Peter Kalauskas Bug: 112488418 Change-Id: I6b58b583e83139eee9f0540da12850c43510cb8e --- drivers/block/zram/zram_drv.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 2dbd39781254..2db2459857fb 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -194,15 +194,17 @@ static bool page_same_filled(void *ptr, unsigned long *element) { 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; } -- 2.20.1