Re: [PATCH] mm/zbud: init user ops only when it is needed

2014-10-18 Thread Dan Streetman 
On Wed, Oct 15, 2014 at 6:00 AM, Heesub Shin  wrote:
> When zbud is initialized through the zpool wrapper, pool->ops which
> points to user-defined operations is always set regardless of whether it
> is specified from the upper layer. This causes zbud_reclaim_page() to
> iterate its loop for evicting pool pages out without any gain.
>
> This patch sets the user-defined ops only when it is needed, so that
> zbud_reclaim_page() can bail out the reclamation loop earlier if there
> is no user-defined operations specified.

Though the only current user (zswap) always passes an ops param, other
future users may not and this is the right way to handle it.  thanks!

>
> Signed-off-by: Heesub Shin 

Acked-by: Dan Streetman 

> ---
>  mm/zbud.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/zbud.c b/mm/zbud.c
> index ecf1dbe..db8de74 100644
> --- a/mm/zbud.c
> +++ b/mm/zbud.c
> @@ -132,7 +132,7 @@ static struct zbud_ops zbud_zpool_ops = {
>
>  static void *zbud_zpool_create(gfp_t gfp, struct zpool_ops *zpool_ops)
>  {
> -   return zbud_create_pool(gfp, _zpool_ops);
> +   return zbud_create_pool(gfp, zpool_ops ? _zpool_ops : NULL);
>  }
>
>  static void zbud_zpool_destroy(void *pool)
> --
> 1.9.1
>
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Re: [PATCH] mm/zbud: init user ops only when it is needed

2014-10-18 Thread Dan Streetman 
On Wed, Oct 15, 2014 at 6:00 AM, Heesub Shin heesub.s...@samsung.com wrote:
 When zbud is initialized through the zpool wrapper, pool-ops which
 points to user-defined operations is always set regardless of whether it
 is specified from the upper layer. This causes zbud_reclaim_page() to
 iterate its loop for evicting pool pages out without any gain.

 This patch sets the user-defined ops only when it is needed, so that
 zbud_reclaim_page() can bail out the reclamation loop earlier if there
 is no user-defined operations specified.

Though the only current user (zswap) always passes an ops param, other
future users may not and this is the right way to handle it.  thanks!


 Signed-off-by: Heesub Shin heesub.s...@samsung.com

Acked-by: Dan Streetman ddstr...@ieee.org

 ---
  mm/zbud.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

 diff --git a/mm/zbud.c b/mm/zbud.c
 index ecf1dbe..db8de74 100644
 --- a/mm/zbud.c
 +++ b/mm/zbud.c
 @@ -132,7 +132,7 @@ static struct zbud_ops zbud_zpool_ops = {

  static void *zbud_zpool_create(gfp_t gfp, struct zpool_ops *zpool_ops)
  {
 -   return zbud_create_pool(gfp, zbud_zpool_ops);
 +   return zbud_create_pool(gfp, zpool_ops ? zbud_zpool_ops : NULL);
  }

  static void zbud_zpool_destroy(void *pool)
 --
 1.9.1

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Re: [PATCH] mm/zbud: init user ops only when it is needed

2014-10-15 Thread Heesub Shin 

Hello,

On 10/16/2014 05:17 AM, Andrew Morton wrote:

On Wed, 15 Oct 2014 19:00:43 +0900 Heesub Shin  wrote:


When zbud is initialized through the zpool wrapper, pool->ops which
points to user-defined operations is always set regardless of whether it
is specified from the upper layer. This causes zbud_reclaim_page() to
iterate its loop for evicting pool pages out without any gain.

This patch sets the user-defined ops only when it is needed, so that
zbud_reclaim_page() can bail out the reclamation loop earlier if there
is no user-defined operations specified.


Which callsite is calling zbud_zpool_create(..., NULL)?


Currently nowhere. zswap is the only user of zbud and always passes a 
pointer to user-defined operation on pool creation. In addition, there 
may be less possibility that pool shrinking is requested by users who 
did not provide the user-defined ops. So, we may not need to worry much 
about what I wrote in the changelog. However, it is definitely weird to 
pass an argument, zpool_ops, which even will not be referenced by 
zbud_zpool_create(). Above all, it would be more useful to avoid the 
possibility in the future rather than just ignoring it.


regards,
heesub




...
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -132,7 +132,7 @@ static struct zbud_ops zbud_zpool_ops = {

  static void *zbud_zpool_create(gfp_t gfp, struct zpool_ops *zpool_ops)
  {
-   return zbud_create_pool(gfp, _zpool_ops);
+   return zbud_create_pool(gfp, zpool_ops ? _zpool_ops : NULL);
  }

  static void zbud_zpool_destroy(void *pool)




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Re: [PATCH] mm/zbud: init user ops only when it is needed

2014-10-15 Thread Andrew Morton 
On Wed, 15 Oct 2014 19:00:43 +0900 Heesub Shin  wrote:

> When zbud is initialized through the zpool wrapper, pool->ops which
> points to user-defined operations is always set regardless of whether it
> is specified from the upper layer. This causes zbud_reclaim_page() to
> iterate its loop for evicting pool pages out without any gain.
> 
> This patch sets the user-defined ops only when it is needed, so that
> zbud_reclaim_page() can bail out the reclamation loop earlier if there
> is no user-defined operations specified.

Which callsite is calling zbud_zpool_create(..., NULL)?

> ...
> --- a/mm/zbud.c
> +++ b/mm/zbud.c
> @@ -132,7 +132,7 @@ static struct zbud_ops zbud_zpool_ops = {
>  
>  static void *zbud_zpool_create(gfp_t gfp, struct zpool_ops *zpool_ops)
>  {
> - return zbud_create_pool(gfp, _zpool_ops);
> + return zbud_create_pool(gfp, zpool_ops ? _zpool_ops : NULL);
>  }
>  
>  static void zbud_zpool_destroy(void *pool)

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[PATCH] mm/zbud: init user ops only when it is needed

2014-10-15 Thread Heesub Shin 
When zbud is initialized through the zpool wrapper, pool->ops which
points to user-defined operations is always set regardless of whether it
is specified from the upper layer. This causes zbud_reclaim_page() to
iterate its loop for evicting pool pages out without any gain.

This patch sets the user-defined ops only when it is needed, so that
zbud_reclaim_page() can bail out the reclamation loop earlier if there
is no user-defined operations specified.

Signed-off-by: Heesub Shin 
---
 mm/zbud.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/zbud.c b/mm/zbud.c
index ecf1dbe..db8de74 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -132,7 +132,7 @@ static struct zbud_ops zbud_zpool_ops = {
 
 static void *zbud_zpool_create(gfp_t gfp, struct zpool_ops *zpool_ops)
 {
-   return zbud_create_pool(gfp, _zpool_ops);
+   return zbud_create_pool(gfp, zpool_ops ? _zpool_ops : NULL);
 }
 
 static void zbud_zpool_destroy(void *pool)
-- 
1.9.1

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[PATCH] mm/zbud: init user ops only when it is needed

2014-10-15 Thread Heesub Shin 
When zbud is initialized through the zpool wrapper, pool-ops which
points to user-defined operations is always set regardless of whether it
is specified from the upper layer. This causes zbud_reclaim_page() to
iterate its loop for evicting pool pages out without any gain.

This patch sets the user-defined ops only when it is needed, so that
zbud_reclaim_page() can bail out the reclamation loop earlier if there
is no user-defined operations specified.

Signed-off-by: Heesub Shin heesub.s...@samsung.com
---
 mm/zbud.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/zbud.c b/mm/zbud.c
index ecf1dbe..db8de74 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -132,7 +132,7 @@ static struct zbud_ops zbud_zpool_ops = {
 
 static void *zbud_zpool_create(gfp_t gfp, struct zpool_ops *zpool_ops)
 {
-   return zbud_create_pool(gfp, zbud_zpool_ops);
+   return zbud_create_pool(gfp, zpool_ops ? zbud_zpool_ops : NULL);
 }
 
 static void zbud_zpool_destroy(void *pool)
-- 
1.9.1

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Re: [PATCH] mm/zbud: init user ops only when it is needed

2014-10-15 Thread Andrew Morton 
On Wed, 15 Oct 2014 19:00:43 +0900 Heesub Shin heesub.s...@samsung.com wrote:

 When zbud is initialized through the zpool wrapper, pool-ops which
 points to user-defined operations is always set regardless of whether it
 is specified from the upper layer. This causes zbud_reclaim_page() to
 iterate its loop for evicting pool pages out without any gain.
 
 This patch sets the user-defined ops only when it is needed, so that
 zbud_reclaim_page() can bail out the reclamation loop earlier if there
 is no user-defined operations specified.

Which callsite is calling zbud_zpool_create(..., NULL)?

 ...
 --- a/mm/zbud.c
 +++ b/mm/zbud.c
 @@ -132,7 +132,7 @@ static struct zbud_ops zbud_zpool_ops = {
  
  static void *zbud_zpool_create(gfp_t gfp, struct zpool_ops *zpool_ops)
  {
 - return zbud_create_pool(gfp, zbud_zpool_ops);
 + return zbud_create_pool(gfp, zpool_ops ? zbud_zpool_ops : NULL);
  }
  
  static void zbud_zpool_destroy(void *pool)

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Re: [PATCH] mm/zbud: init user ops only when it is needed

2014-10-15 Thread Heesub Shin 

Hello,

On 10/16/2014 05:17 AM, Andrew Morton wrote:

On Wed, 15 Oct 2014 19:00:43 +0900 Heesub Shin heesub.s...@samsung.com wrote:


When zbud is initialized through the zpool wrapper, pool-ops which
points to user-defined operations is always set regardless of whether it
is specified from the upper layer. This causes zbud_reclaim_page() to
iterate its loop for evicting pool pages out without any gain.

This patch sets the user-defined ops only when it is needed, so that
zbud_reclaim_page() can bail out the reclamation loop earlier if there
is no user-defined operations specified.


Which callsite is calling zbud_zpool_create(..., NULL)?


Currently nowhere. zswap is the only user of zbud and always passes a 
pointer to user-defined operation on pool creation. In addition, there 
may be less possibility that pool shrinking is requested by users who 
did not provide the user-defined ops. So, we may not need to worry much 
about what I wrote in the changelog. However, it is definitely weird to 
pass an argument, zpool_ops, which even will not be referenced by 
zbud_zpool_create(). Above all, it would be more useful to avoid the 
possibility in the future rather than just ignoring it.


regards,
heesub




...
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -132,7 +132,7 @@ static struct zbud_ops zbud_zpool_ops = {

  static void *zbud_zpool_create(gfp_t gfp, struct zpool_ops *zpool_ops)
  {
-   return zbud_create_pool(gfp, zbud_zpool_ops);
+   return zbud_create_pool(gfp, zpool_ops ? zbud_zpool_ops : NULL);
  }

  static void zbud_zpool_destroy(void *pool)




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