[RFC][PATCHv3 2/7] zsmalloc: partial page ordering within a fullness_list

Sergey Senozhatsky
2015-06-18T11:49:29Z

We want to see more ZS_FULL pages and less ZS_ALMOST_{FULL, EMPTY}
pages. Put a page with higher ->inuse count first within its
->fullness_list, which will give us better chances to fill up this
page with new objects (find_get_zspage() return ->fullness_list head
for new object allocation), so some zspages will become
ZS_ALMOST_FULL/ZS_FULL quicker.

It performs a trivial and cheap ->inuse compare which does not slow
down zsmalloc, and in the worst case it keeps the list pages not in
any particular order, just like we do it now.

A more expensive solution could sort fullness_list by ->inuse count.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
mm/zsmalloc.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 7d816c2..6e2ebb6 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -659,8 +659,16 @@ static void insert_zspage(struct page *page, struct size_class *class,
return;

head = &class->fullness_list[fullness];
- if (*head)
- list_add_tail(&page->lru, &(*head)->lru);
+ if (*head) {
+ /*
+ * We want to see more ZS_FULL pages and less almost
+ * empty/full. Put pages with higher ->inuse first.
+ */
+ if (page->inuse < (*head)->inuse)
+ list_add_tail(&page->lru, &(*head)->lru);
+ else
+ list_add(&page->lru, &(*head)->lru);
+ }

*head = page;
zs_stat_inc(class, fullness == ZS_ALMOST_EMPTY ?
--
2.4.4