Commit 22c5cef1 authored Feb 24, 2017 by Yisheng Xie Committed by Linus Torvalds Feb 24, 2017

mm/zsmalloc: remove redundant SetPagePrivate2 in create_page_chain

We had used page->lru to link the component pages (except the first
page) of a zspage, and used INIT_LIST_HEAD(&page->lru) to init it.
Therefore, to get the last page's next page, which is NULL, we had to
use page flag PG_Private_2 to identify it.

But now, we use page->freelist to link all of the pages in zspage and
init the page->freelist as NULL for last page, so no need to use
PG_Private_2 anymore.

This remove redundant SetPagePrivate2 in create_page_chain and
ClearPagePrivate2 in reset_page().  Save a few cycles for migration of
zsmalloc page :)

Link: http://lkml.kernel.org/r/1487076509-49270-1-git-send-email-xieyisheng1@huawei.com


Signed-off-by: Yisheng Xie <xieyisheng1@huawei.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>

parent e1587a49

mm/zsmalloc.c

+1 −5

Original line number	Diff line number	Diff line
		@@ -24,7 +24,6 @@
		*
		* Usage of struct page flags:
		* PG_private: identifies the first component page
		* PG_private2: identifies the last component page
		* PG_owner_priv_1: identifies the huge component page
		*
		*/
		@@ -938,7 +937,6 @@ static void reset_page(struct page *page)
		{
		__ClearPageMovable(page);
		ClearPagePrivate(page);
		ClearPagePrivate2(page);
		set_page_private(page, 0);
		page_mapcount_reset(page);
		ClearPageHugeObject(page);
		@@ -1085,7 +1083,7 @@ static void create_page_chain(struct size_class class, struct zspage zspage,
		* 2. each sub-page point to zspage using page->private
		*
		* we set PG_private to identify the first page (i.e. no other sub-page
		* has this flag set) and PG_private_2 to identify the last page.
		* has this flag set).
		*/
		for (i = 0; i < nr_pages; i++) {
		page = pages[i];
		@@ -1100,8 +1098,6 @@ static void create_page_chain(struct size_class class, struct zspage zspage,
		} else {
		prev_page->freelist = page;
		}
		if (i == nr_pages - 1)
		SetPagePrivate2(page);
		prev_page = page;
		}
		}

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