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UPSTREAM: zram: reduce load operation in page_same_filled

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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 f0fe998465)
Signed-off-by: Peter Kalauskas <peskal@google.com>
Bug: 112488418
Change-Id: I6b58b583e83139eee9f0540da12850c43510cb8e
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
This commit is contained in:
Sangwoo Park 2017-05-03 14:55:56 -07:00 committed by Amit Pundir
parent 12306d58fe
commit 88befbacdb
1 changed files with 5 additions and 3 deletions
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8
drivers/block/zram/zram_drv.c
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@ -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;
}