2014-11-20 13:08:51

by Ganesh Mahendran

Subject: [PATCH] mm/zsmalloc: avoid duplicate assignment of prev_class

In zs_create_pool(), prev_class is assigned (ZS_SIZE_CLASSES - 1)
times. And the prev_class only references to the previous alloc
size_class. So we do not need unnecessary assignement.

This patch modifies *prev_class* to *prev_alloc_class*. And the
*prev_alloc_class* will only be assigned when a new size_class
structure is allocated.

Signed-off-by: Mahendran Ganesh <[email protected]>
---
mm/zsmalloc.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index b3b57ef..ac2b396 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -970,7 +970,7 @@ struct zs_pool *zs_create_pool(gfp_t flags)
int size;
int pages_per_zspage;
struct size_class *class;
- struct size_class *prev_class;
+ struct size_class *uninitialized_var(prev_alloc_class);

size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
if (size > ZS_MAX_ALLOC_SIZE)
@@ -987,9 +987,8 @@ struct zs_pool *zs_create_pool(gfp_t flags)
* previous size_class if possible.
*/
if (i < ZS_SIZE_CLASSES - 1) {
- prev_class = pool->size_class[i + 1];
- if (can_merge(prev_class, size, pages_per_zspage)) {
- pool->size_class[i] = prev_class;
+ if (can_merge(prev_alloc_class, size, pages_per_zspage)) {
+ pool->size_class[i] = prev_alloc_class;
continue;
}
}
@@ -1003,6 +1002,8 @@ struct zs_pool *zs_create_pool(gfp_t flags)
class->pages_per_zspage = pages_per_zspage;
spin_lock_init(&class->lock);
pool->size_class[i] = class;
+
+ prev_alloc_class = class;
}

pool->flags = flags;
--
1.7.9.5

2014-11-21 03:22:42

by Dan Streetman

Subject: Re: [PATCH] mm/zsmalloc: avoid duplicate assignment of prev_class

On Thu, Nov 20, 2014 at 8:08 AM, Mahendran Ganesh
<[email protected]> wrote:
> In zs_create_pool(), prev_class is assigned (ZS_SIZE_CLASSES - 1)
> times. And the prev_class only references to the previous alloc
> size_class. So we do not need unnecessary assignement.
>
> This patch modifies *prev_class* to *prev_alloc_class*. And the
> *prev_alloc_class* will only be assigned when a new size_class
> structure is allocated.
>
> Signed-off-by: Mahendran Ganesh <[email protected]>
> ---
> mm/zsmalloc.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index b3b57ef..ac2b396 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -970,7 +970,7 @@ struct zs_pool *zs_create_pool(gfp_t flags)
> int size;
> int pages_per_zspage;
> struct size_class *class;
> - struct size_class *prev_class;
> + struct size_class *uninitialized_var(prev_alloc_class);

+ struct size_class *prev_class = NULL;

Use the fact it's unset below, so set it to NULL here

>
> size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
> if (size > ZS_MAX_ALLOC_SIZE)
> @@ -987,9 +987,8 @@ struct zs_pool *zs_create_pool(gfp_t flags)
> * previous size_class if possible.
> */
> if (i < ZS_SIZE_CLASSES - 1) {
> - prev_class = pool->size_class[i + 1];
> - if (can_merge(prev_class, size, pages_per_zspage)) {
> - pool->size_class[i] = prev_class;
> + if (can_merge(prev_alloc_class, size, pages_per_zspage)) {
> + pool->size_class[i] = prev_alloc_class;

simplify more, we can check if this is the first iteration by looking
at prev_class, e.g.:

if (prev_class) {
if (can_merge(prev_class, size, pages_per_zspage)) {
pool->size_class[i] = prev_class;


> continue;
> }
> }
> @@ -1003,6 +1002,8 @@ struct zs_pool *zs_create_pool(gfp_t flags)
> class->pages_per_zspage = pages_per_zspage;
> spin_lock_init(&class->lock);
> pool->size_class[i] = class;
> +
> + prev_alloc_class = class;
> }
>
> pool->flags = flags;
> --
> 1.7.9.5
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to [email protected]. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"[email protected]"> [email protected] </a>

2014-11-21 03:43:51

by Minchan Kim

Subject: Re: [PATCH] mm/zsmalloc: avoid duplicate assignment of prev_class

On Thu, Nov 20, 2014 at 09:08:33PM +0800, Mahendran Ganesh wrote:
> In zs_create_pool(), prev_class is assigned (ZS_SIZE_CLASSES - 1)
> times. And the prev_class only references to the previous alloc
> size_class. So we do not need unnecessary assignement.
>
> This patch modifies *prev_class* to *prev_alloc_class*. And the
> *prev_alloc_class* will only be assigned when a new size_class
> structure is allocated.
>
> Signed-off-by: Mahendran Ganesh <[email protected]>
> ---
> mm/zsmalloc.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index b3b57ef..ac2b396 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -970,7 +970,7 @@ struct zs_pool *zs_create_pool(gfp_t flags)
> int size;
> int pages_per_zspage;
> struct size_class *class;
> - struct size_class *prev_class;
> + struct size_class *uninitialized_var(prev_alloc_class);

https://lkml.org/lkml/2012/10/27/71
In addition, I prefer prev_class.

Thanks.

--
Kind regards,
Minchan Kim

2014-11-21 05:22:23

by Ganesh Mahendran

Subject: Re: [PATCH] mm/zsmalloc: avoid duplicate assignment of prev_class

Hello

2014-11-21 11:22 GMT+08:00 Dan Streetman <[email protected]>:
> On Thu, Nov 20, 2014 at 8:08 AM, Mahendran Ganesh
> <[email protected]> wrote:
>> In zs_create_pool(), prev_class is assigned (ZS_SIZE_CLASSES - 1)
>> times. And the prev_class only references to the previous alloc
>> size_class. So we do not need unnecessary assignement.
>>
>> This patch modifies *prev_class* to *prev_alloc_class*. And the
>> *prev_alloc_class* will only be assigned when a new size_class
>> structure is allocated.
>>
>> Signed-off-by: Mahendran Ganesh <[email protected]>
>> ---
>> mm/zsmalloc.c | 9 +++++----
>> 1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
>> index b3b57ef..ac2b396 100644
>> --- a/mm/zsmalloc.c
>> +++ b/mm/zsmalloc.c
>> @@ -970,7 +970,7 @@ struct zs_pool *zs_create_pool(gfp_t flags)
>> int size;
>> int pages_per_zspage;
>> struct size_class *class;
>> - struct size_class *prev_class;
>> + struct size_class *uninitialized_var(prev_alloc_class);
>
> + struct size_class *prev_class = NULL;
>
> Use the fact it's unset below, so set it to NULL here

Yes, You are right. I will change it in next resend.
Thanks for your review.

>
>>
>> size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
>> if (size > ZS_MAX_ALLOC_SIZE)
>> @@ -987,9 +987,8 @@ struct zs_pool *zs_create_pool(gfp_t flags)
>> * previous size_class if possible.
>> */
>> if (i < ZS_SIZE_CLASSES - 1) {
>> - prev_class = pool->size_class[i + 1];
>> - if (can_merge(prev_class, size, pages_per_zspage)) {
>> - pool->size_class[i] = prev_class;
>> + if (can_merge(prev_alloc_class, size, pages_per_zspage)) {
>> + pool->size_class[i] = prev_alloc_class;
>
> simplify more, we can check if this is the first iteration by looking
> at prev_class, e.g.:
>
> if (prev_class) {
> if (can_merge(prev_class, size, pages_per_zspage)) {
> pool->size_class[i] = prev_class;
>
>
>> continue;
>> }
>> }
>> @@ -1003,6 +1002,8 @@ struct zs_pool *zs_create_pool(gfp_t flags)
>> class->pages_per_zspage = pages_per_zspage;
>> spin_lock_init(&class->lock);
>> pool->size_class[i] = class;
>> +
>> + prev_alloc_class = class;
>> }
>>
>> pool->flags = flags;
>> --
>> 1.7.9.5
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to [email protected]. For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"[email protected]"> [email protected] </a>

2014-11-21 05:25:39

by Ganesh Mahendran

Subject: Re: [PATCH] mm/zsmalloc: avoid duplicate assignment of prev_class

Hello

2014-11-21 11:43 GMT+08:00 Minchan Kim <[email protected]>:
> On Thu, Nov 20, 2014 at 09:08:33PM +0800, Mahendran Ganesh wrote:
>> In zs_create_pool(), prev_class is assigned (ZS_SIZE_CLASSES - 1)
>> times. And the prev_class only references to the previous alloc
>> size_class. So we do not need unnecessary assignement.
>>
>> This patch modifies *prev_class* to *prev_alloc_class*. And the
>> *prev_alloc_class* will only be assigned when a new size_class
>> structure is allocated.
>>
>> Signed-off-by: Mahendran Ganesh <[email protected]>
>> ---
>> mm/zsmalloc.c | 9 +++++----
>> 1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
>> index b3b57ef..ac2b396 100644
>> --- a/mm/zsmalloc.c
>> +++ b/mm/zsmalloc.c
>> @@ -970,7 +970,7 @@ struct zs_pool *zs_create_pool(gfp_t flags)
>> int size;
>> int pages_per_zspage;
>> struct size_class *class;
>> - struct size_class *prev_class;
>> + struct size_class *uninitialized_var(prev_alloc_class);
>
> https://lkml.org/lkml/2012/10/27/71
> In addition, I prefer prev_class.

Thanks for you review. I will resend the patch.

>
> Thanks.
>
> --
> Kind regards,
> Minchan Kim