diff mbox

[3/6] swap: Unify normal/huge code path in swap_page_trans_huge_swapped()

Message ID 20180712233636.20629-4-ying.huang@intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Huang, Ying July 12, 2018, 11:36 p.m. UTC 
From: Huang Ying <ying.huang@intel.com>

As suggested by Dave, we should unify the code path for normal and
huge swap support if possible to avoid duplicated code, bugs, etc. and
make it easier to review code.

In this patch, the normal/huge code path in swap_page_trans_huge_swapped()
is unified, the added and removed lines are same.  And the binary size
is kept almost same when CONFIG_TRANSPARENT_HUGEPAGE=n.

		 text	   data	    bss	    dec	    hex	filename
base:		24179	   2028	    340	  26547	   67b3	mm/swapfile.o
unified:	24215	   2028	    340	  26583	   67d7	mm/swapfile.o

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Dan Williams <dan.j.williams@intel.com>
---
 mm/swapfile.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Comments

Daniel Jordan July 13, 2018, 8:15 p.m. UTC | #1 
On Fri, Jul 13, 2018 at 07:36:33AM +0800, Huang, Ying wrote:
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 75c84aa763a3..160f78072667 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -270,7 +270,10 @@ static inline void cluster_set_null(struct swap_cluster_info *info)
>  
>  static inline bool cluster_is_huge(struct swap_cluster_info *info)
>  {
> -	return info->flags & CLUSTER_FLAG_HUGE;
> +	if (IS_ENABLED(CONFIG_THP_SWAP))
> +		return info->flags & CLUSTER_FLAG_HUGE;
> +	else
> +		return false;
>  }
>  
>  static inline void cluster_clear_huge(struct swap_cluster_info *info)
> @@ -1489,9 +1492,6 @@ static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
>  	int i;
>  	bool ret = false;
>  
> -	if (!IS_ENABLED(CONFIG_THP_SWAP))
> -		return swap_swapcount(si, entry) != 0;

This tests the value returned from swap_count,

> -
>  	ci = lock_cluster_or_swap_info(si, offset);
>  	if (!ci || !cluster_is_huge(ci)) {
>  		if (map[roffset] != SWAP_HAS_CACHE)

and now we're testing

                    map[roffset] != SWAP_HAS_CACHE

instead.  The two seem to mean the same thing here, since the swap slot hasn't
been freed to the global pool and so can't be 0, but it might be better for
consistency and clarity to use swap_count here, and a few lines down too

        for (i = 0; i < SWAPFILE_CLUSTER; i++) {                                     
                if (map[offset + i] != SWAP_HAS_CACHE) {                             

since swap_count seems to be used everywhere else for this.
Huang, Ying July 14, 2018, 12:53 p.m. UTC | #2 
Daniel Jordan <daniel.m.jordan@oracle.com> writes:

> On Fri, Jul 13, 2018 at 07:36:33AM +0800, Huang, Ying wrote:
>> diff --git a/mm/swapfile.c b/mm/swapfile.c
>> index 75c84aa763a3..160f78072667 100644
>> --- a/mm/swapfile.c
>> +++ b/mm/swapfile.c
>> @@ -270,7 +270,10 @@ static inline void cluster_set_null(struct swap_cluster_info *info)
>>  
>>  static inline bool cluster_is_huge(struct swap_cluster_info *info)
>>  {
>> -	return info->flags & CLUSTER_FLAG_HUGE;
>> +	if (IS_ENABLED(CONFIG_THP_SWAP))
>> +		return info->flags & CLUSTER_FLAG_HUGE;
>> +	else
>> +		return false;
>>  }
>>  
>>  static inline void cluster_clear_huge(struct swap_cluster_info *info)
>> @@ -1489,9 +1492,6 @@ static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
>>  	int i;
>>  	bool ret = false;
>>  
>> -	if (!IS_ENABLED(CONFIG_THP_SWAP))
>> -		return swap_swapcount(si, entry) != 0;
>
> This tests the value returned from swap_count,
>
>> -
>>  	ci = lock_cluster_or_swap_info(si, offset);
>>  	if (!ci || !cluster_is_huge(ci)) {
>>  		if (map[roffset] != SWAP_HAS_CACHE)
>
> and now we're testing
>
>                     map[roffset] != SWAP_HAS_CACHE
>
> instead.  The two seem to mean the same thing here, since the swap slot hasn't
> been freed to the global pool and so can't be 0, but it might be better for
> consistency and clarity to use swap_count here, and a few lines down too
>
>         for (i = 0; i < SWAPFILE_CLUSTER; i++) {                                     
>                 if (map[offset + i] != SWAP_HAS_CACHE) {                             
>
> since swap_count seems to be used everywhere else for this.

Yes.  swap_count() looks better here.  Will change this.

Best Regards,
Huang, Ying
diff mbox

Patch

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 75c84aa763a3..160f78072667 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -270,7 +270,10 @@  static inline void cluster_set_null(struct swap_cluster_info *info)
 
 static inline bool cluster_is_huge(struct swap_cluster_info *info)
 {
-	return info->flags & CLUSTER_FLAG_HUGE;
+	if (IS_ENABLED(CONFIG_THP_SWAP))
+		return info->flags & CLUSTER_FLAG_HUGE;
+	else
+		return false;
 }
 
 static inline void cluster_clear_huge(struct swap_cluster_info *info)
@@ -1489,9 +1492,6 @@  static bool swap_page_trans_huge_swapped(struct swap_info_struct *si,
 	int i;
 	bool ret = false;
 
-	if (!IS_ENABLED(CONFIG_THP_SWAP))
-		return swap_swapcount(si, entry) != 0;
-
 	ci = lock_cluster_or_swap_info(si, offset);
 	if (!ci || !cluster_is_huge(ci)) {
 		if (map[roffset] != SWAP_HAS_CACHE)