[PATCH v2 0/2] Fix and Enhance deactive_page

[PATCH v2 0/2] Fix and Enhance deactive_page

[Minchan Kim]

A few days ago, Ying reported a problem.
http://marc.info/?l=linux-mm&m=130403310601663&w=2
After I and Ying dive in problem, We found deactive_page
has a problem. Apparently, It's a BUG so 
[1/2] is fix of the problem and [2/2] is enhancement for 
helping CPU.

* v2
  - add Reviewed-by signs
  - Fix typo

Minchan Kim (2):
  [1/2] Check PageUnevictable in lru_deactivate_fn
  [2/2] Filter unevictable page out in deactivate_page

 mm/swap.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

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[PATCH v2 1/2] Check PageUnevictable in lru_deactivate_fn

[Minchan Kim]

The lru_deactivate_fn should not move page which in on unevictable lru
into inactive list. Otherwise, we can meet BUG when we use isolate_lru_pages
as __isolate_lru_page could return -EINVAL.
It's really BUG and let's fix it.

Reported-by: Ying Han <yinghan@google.com>
Tested-by: Ying Han <yinghan@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Rik van Riel<riel@redhat.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
---
 mm/swap.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/mm/swap.c b/mm/swap.c
index a83ec5a..2e9656d 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -429,6 +429,9 @@ static void lru_deactivate_fn(struct page *page, void *arg)
 	if (!PageLRU(page))
 		return;
 
+	if (PageUnevictable(page))
+		return;
+
 	/* Some processes are using the page */
 	if (page_mapped(page))
 		return;
-- 
1.7.1

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[PATCH v2 2/2] Filter unevictable page out in deactivate_page

[Minchan Kim]

It's pointless that deactive_page's pagevec operation about
unevictable page as it's nop.
This patch removes unnecessary overhead which might be a bit problem
in case that there are many unevictable page in system(ex, mprotect workload)

Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
---
 mm/swap.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/mm/swap.c b/mm/swap.c
index 2e9656d..e121ceb 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -511,6 +511,15 @@ static void drain_cpu_pagevecs(int cpu)
  */
 void deactivate_page(struct page *page)
 {
+
+	/*
+	 * In workload which system has many unevictable page(ex, mprotect),
+	 * unevictable page deactivation for accelerating reclaim
+	 * is pointless.
+	 */
+	if (PageUnevictable(page))
+		return;
+
 	if (likely(get_page_unless_zero(page))) {
 		struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
 
-- 
1.7.1

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Re: [PATCH v2 2/2] Filter unevictable page out in deactivate_page

[Rik van Riel]

On 05/03/2011 10:48 AM, Minchan Kim wrote:
> It's pointless that deactive_page's pagevec operation about
> unevictable page as it's nop.
> This patch removes unnecessary overhead which might be a bit problem
> in case that there are many unevictable page in system(ex, mprotect workload)
>
> Reviewed-by: KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: Minchan Kim<minchan.kim@gmail.com>

Reviewed-by: Rik van Riel<riel@redhat.com>

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