[PATCH 0/2] Fix an enhance deactive_page

[PATCH 0/2] Fix an 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.


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 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>
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 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)

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..b707694 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),
+	 * unevictalge 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 1/2] Check PageUnevictable in lru_deactivate_fn

[Ying Han]

On Sun, May 1, 2011 at 8:03 AM, Minchan Kim <minchan.kim@gmail.com> wrote:
> 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>
> 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

Thanks Minchan for the fix, and i haven't been able to reproducing the
issue after applying the patch.

--Ying

>

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Re: [PATCH 1/2] Check PageUnevictable in lru_deactivate_fn

[Minchan Kim]

On Mon, May 2, 2011 at 7:10 AM, Ying Han <yinghan@google.com> wrote:
> On Sun, May 1, 2011 at 8:03 AM, Minchan Kim <minchan.kim@gmail.com> wrote:
>> 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>
>> 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
>
> Thanks Minchan for the fix, and i haven't been able to reproducing the
> issue after applying the patch.

Thanks for the help, Ying.

-- 
Kind regards,
Minchan Kim

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Re: [PATCH 1/2] Check PageUnevictable in lru_deactivate_fn

[KOSAKI Motohiro]

> 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>
> 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;
> +

	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>



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

[KOSAKI Motohiro]

> 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)
> 
> 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..b707694 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),
> +	 * unevictalge page deactivation for accelerating reclaim
> +	 * is pointless.
> +	 */
> +	if (PageUnevictable(page))
> +		return;
> +

	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>


btw, I think we should check PageLRU too.



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Re: [PATCH 1/2] Check PageUnevictable in lru_deactivate_fn

[Rik van Riel]

On 05/01/2011 11:03 AM, Minchan Kim wrote:
> 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>
> Signed-off-by: Minchan Kim<minchan.kim@gmail.com>

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

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

[Rik van Riel]

On 05/01/2011 11:03 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)
>
> 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..b707694 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),
> +	 * unevictalge page deactivation for accelerating reclaim

Typo.

> +	 * is pointless.
> +	 */
> +	if (PageUnevictable(page))
> +		return;
> +
>   	if (likely(get_page_unless_zero(page))) {
>   		struct pagevec *pvec =&get_cpu_var(lru_deactivate_pvecs);
>


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

[Minchan Kim]

Hi KOSAKI,

On Mon, May 2, 2011 at 7:37 PM, KOSAKI Motohiro
<kosaki.motohiro@jp.fujitsu.com> 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)
>>
>> 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..b707694 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),
>> +      * unevictalge page deactivation for accelerating reclaim
>> +      * is pointless.
>> +      */
>> +     if (PageUnevictable(page))
>> +             return;
>> +
>
>        Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>

Thanks!

>
> btw, I think we should check PageLRU too.
>

Yes. I remember you advised it when we push this patch but I didn't.
That's because I think most of pages in such context would be LRU as
they are cached pages.
So IMO, PageLRU checking in deactivate_page couldn't help much.


-- 
Kind regards,
Minchan Kim

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

[Minchan Kim]

Hi Rik,

On Mon, May 2, 2011 at 11:57 PM, Rik van Riel <riel@redhat.com> wrote:
> On 05/01/2011 11:03 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)
>>
>> 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..b707694 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),
>> +        * unevictalge page deactivation for accelerating reclaim
>
> Typo.

My bad. I will resend after work.
Thanks.

-- 
Kind regards,
Minchan Kim

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