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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>
This commit is contained in:
Sangwoo Park 2017-05-03 14:55:56 -07:00 committed by Linus Torvalds
parent 302128dce1
commit f0fe998465
1 changed files with 5 additions and 3 deletions
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8
drivers/block/zram/zram_drv.c
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@ -195,15 +195,17 @@ 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;
}