[PATCH V2] mm/damon: simplify scheme create in lru_sort.c

[PATCH V2] mm/damon: simplify scheme create in lru_sort.c

[Xin Hao]

In damon_lru_sort_new_hot_scheme() and damon_lru_sort_new_cold_scheme(),
they have so much in common, so we can combine them into a single
function, and we just need to distinguish their differences.

Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
---
 mm/damon/lru_sort.c | 57 ++++++++++++++++++++++-----------------------
 1 file changed, 28 insertions(+), 29 deletions(-)

diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
index 07a0908963fd..2eac907e866d 100644
--- a/mm/damon/lru_sort.c
+++ b/mm/damon/lru_sort.c
@@ -135,17 +135,40 @@ DEFINE_DAMON_MODULES_DAMOS_STATS_PARAMS(damon_lru_sort_cold_stat,
 static struct damon_ctx *ctx;
 static struct damon_target *target;
 
-static struct damos *damon_lru_sort_new_scheme(
-		struct damos_access_pattern *pattern, enum damos_action action)
+static struct damos *damon_lru_sort_new_scheme(unsigned int thres,
+					       enum damos_action action)
 {
+	struct damos_access_pattern pattern = {
+		/* Find regions having PAGE_SIZE or larger size */
+		.min_sz_region = PAGE_SIZE,
+		.max_sz_region = ULONG_MAX,
+		/* and accessed for more than the threshold */
+		.min_nr_accesses = 0,
+		.max_nr_accesses = 0,
+		/* no matter its age */
+		.min_age_region = 0,
+		.max_age_region = UINT_MAX,
+	};
 	struct damos_quota quota = damon_lru_sort_quota;
 
 	/* Use half of total quota for hot/cold pages sorting */
 	quota.ms = quota.ms / 2;
 
+	switch (action) {
+	case DAMOS_LRU_PRIO:
+		pattern.min_nr_accesses = thres;
+		pattern.max_nr_accesses = UINT_MAX;
+		break;
+	case DAMOS_LRU_DEPRIO:
+		pattern.min_age_region = thres;
+		break;
+	default:
+		return NULL;
+	}
+
 	return damon_new_scheme(
 			/* find the pattern, and */
-			pattern,
+			&pattern,
 			/* (de)prioritize on LRU-lists */
 			action,
 			/* under the quota. */
@@ -157,37 +180,13 @@ static struct damos *damon_lru_sort_new_scheme(
 /* Create a DAMON-based operation scheme for hot memory regions */
 static struct damos *damon_lru_sort_new_hot_scheme(unsigned int hot_thres)
 {
-	struct damos_access_pattern pattern = {
-		/* Find regions having PAGE_SIZE or larger size */
-		.min_sz_region = PAGE_SIZE,
-		.max_sz_region = ULONG_MAX,
-		/* and accessed for more than the threshold */
-		.min_nr_accesses = hot_thres,
-		.max_nr_accesses = UINT_MAX,
-		/* no matter its age */
-		.min_age_region = 0,
-		.max_age_region = UINT_MAX,
-	};
-
-	return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_PRIO);
+	return damon_lru_sort_new_scheme(hot_thres, DAMOS_LRU_PRIO);
 }
 
 /* Create a DAMON-based operation scheme for cold memory regions */
 static struct damos *damon_lru_sort_new_cold_scheme(unsigned int cold_thres)
 {
-	struct damos_access_pattern pattern = {
-		/* Find regions having PAGE_SIZE or larger size */
-		.min_sz_region = PAGE_SIZE,
-		.max_sz_region = ULONG_MAX,
-		/* and not accessed at all */
-		.min_nr_accesses = 0,
-		.max_nr_accesses = 0,
-		/* for min_age or more micro-seconds */
-		.min_age_region = cold_thres,
-		.max_age_region = UINT_MAX,
-	};
-
-	return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_DEPRIO);
+	return damon_lru_sort_new_scheme(cold_thres, DAMOS_LRU_DEPRIO);
 }
 
 static int damon_lru_sort_apply_parameters(void)
-- 
2.31.0

Re: [PATCH V2] mm/damon: simplify scheme create in lru_sort.c

[SeongJae Park]

Hi Xin,

On Wed, 14 Sep 2022 19:38:59 +0800 Xin Hao <xhao@linux.alibaba.com> wrote:

> In damon_lru_sort_new_hot_scheme() and damon_lru_sort_new_cold_scheme(),
> they have so much in common, so we can combine them into a single
> function, and we just need to distinguish their differences.

Thank you again for patiently waiting for my changes and reworking on this!

> 
> Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
> ---
>  mm/damon/lru_sort.c | 57 ++++++++++++++++++++++-----------------------
>  1 file changed, 28 insertions(+), 29 deletions(-)
> 
> diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
> index 07a0908963fd..2eac907e866d 100644
> --- a/mm/damon/lru_sort.c
> +++ b/mm/damon/lru_sort.c
> @@ -135,17 +135,40 @@ DEFINE_DAMON_MODULES_DAMOS_STATS_PARAMS(damon_lru_sort_cold_stat,
>  static struct damon_ctx *ctx;
>  static struct damon_target *target;
>  
> -static struct damos *damon_lru_sort_new_scheme(
> -		struct damos_access_pattern *pattern, enum damos_action action)
> +static struct damos *damon_lru_sort_new_scheme(unsigned int thres,
> +					       enum damos_action action)
>  {
> +	struct damos_access_pattern pattern = {
> +		/* Find regions having PAGE_SIZE or larger size */
> +		.min_sz_region = PAGE_SIZE,
> +		.max_sz_region = ULONG_MAX,
> +		/* and accessed for more than the threshold */

This comment would be better to be written again?

> +		.min_nr_accesses = 0,
> +		.max_nr_accesses = 0,

If we're gonna set above two fields anyway later, we could simply remove above
three lines.

> +		/* no matter its age */
> +		.min_age_region = 0,
> +		.max_age_region = UINT_MAX,
> +	};
>  	struct damos_quota quota = damon_lru_sort_quota;
>  
>  	/* Use half of total quota for hot/cold pages sorting */
>  	quota.ms = quota.ms / 2;
>  
> +	switch (action) {
> +	case DAMOS_LRU_PRIO:
> +		pattern.min_nr_accesses = thres;
> +		pattern.max_nr_accesses = UINT_MAX;
> +		break;
> +	case DAMOS_LRU_DEPRIO:
> +		pattern.min_age_region = thres;
> +		break;
> +	default:
> +		return NULL;
> +	}
> +

This switch-case makes me wondering if the 'default' case really possible case.
I think it would be clearer to set these from caller.

IMHO, it might be clearer and shorter to define a static global 'struct
damos_access_pattern' stub variable, and make the
damon_lru_sort_new_{hot,cold}_scheme() copies it to their local variable,
update the relevant fields, and pass that to 'damon_new_scheme()'.  What do you
think?

>  	return damon_new_scheme(
>  			/* find the pattern, and */
> -			pattern,
> +			&pattern,
>  			/* (de)prioritize on LRU-lists */
>  			action,
>  			/* under the quota. */
> @@ -157,37 +180,13 @@ static struct damos *damon_lru_sort_new_scheme(
>  /* Create a DAMON-based operation scheme for hot memory regions */
>  static struct damos *damon_lru_sort_new_hot_scheme(unsigned int hot_thres)
>  {
> -	struct damos_access_pattern pattern = {
> -		/* Find regions having PAGE_SIZE or larger size */
> -		.min_sz_region = PAGE_SIZE,
> -		.max_sz_region = ULONG_MAX,
> -		/* and accessed for more than the threshold */
> -		.min_nr_accesses = hot_thres,
> -		.max_nr_accesses = UINT_MAX,
> -		/* no matter its age */
> -		.min_age_region = 0,
> -		.max_age_region = UINT_MAX,
> -	};
> -
> -	return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_PRIO);
> +	return damon_lru_sort_new_scheme(hot_thres, DAMOS_LRU_PRIO);

If we follow what I suggested above, we could make this like below:

	struct damos_access_pattern pattern = damon_lru_sort_stub_access_pattern;

	pattern.min_nr_accesses = hot_thres;
	return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_PRIO);


>  }
>  
>  /* Create a DAMON-based operation scheme for cold memory regions */
>  static struct damos *damon_lru_sort_new_cold_scheme(unsigned int cold_thres)
>  {
> -	struct damos_access_pattern pattern = {
> -		/* Find regions having PAGE_SIZE or larger size */
> -		.min_sz_region = PAGE_SIZE,
> -		.max_sz_region = ULONG_MAX,
> -		/* and not accessed at all */
> -		.min_nr_accesses = 0,
> -		.max_nr_accesses = 0,
> -		/* for min_age or more micro-seconds */
> -		.min_age_region = cold_thres,
> -		.max_age_region = UINT_MAX,
> -	};
> -
> -	return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_DEPRIO);
> +	return damon_lru_sort_new_scheme(cold_thres, DAMOS_LRU_DEPRIO);

And similarly here.

>  }
>  
>  static int damon_lru_sort_apply_parameters(void)
> -- 
> 2.31.0
> 
> 


Thanks,
SJ

Re: [PATCH V2] mm/damon: simplify scheme create in lru_sort.c

[haoxin]

在 2022/9/14 下午10:22, SeongJae Park 写道:
> Hi Xin,
>
> On Wed, 14 Sep 2022 19:38:59 +0800 Xin Hao <xhao@linux.alibaba.com> wrote:
>
>> In damon_lru_sort_new_hot_scheme() and damon_lru_sort_new_cold_scheme(),
>> they have so much in common, so we can combine them into a single
>> function, and we just need to distinguish their differences.
> Thank you again for patiently waiting for my changes and reworking on this!
>
>> Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
>> ---
>>   mm/damon/lru_sort.c | 57 ++++++++++++++++++++++-----------------------
>>   1 file changed, 28 insertions(+), 29 deletions(-)
>>
>> diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
>> index 07a0908963fd..2eac907e866d 100644
>> --- a/mm/damon/lru_sort.c
>> +++ b/mm/damon/lru_sort.c
>> @@ -135,17 +135,40 @@ DEFINE_DAMON_MODULES_DAMOS_STATS_PARAMS(damon_lru_sort_cold_stat,
>>   static struct damon_ctx *ctx;
>>   static struct damon_target *target;
>>   
>> -static struct damos *damon_lru_sort_new_scheme(
>> -		struct damos_access_pattern *pattern, enum damos_action action)
>> +static struct damos *damon_lru_sort_new_scheme(unsigned int thres,
>> +					       enum damos_action action)
>>   {
>> +	struct damos_access_pattern pattern = {
>> +		/* Find regions having PAGE_SIZE or larger size */
>> +		.min_sz_region = PAGE_SIZE,
>> +		.max_sz_region = ULONG_MAX,
>> +		/* and accessed for more than the threshold */
> This comment would be better to be written again?
>
>> +		.min_nr_accesses = 0,
>> +		.max_nr_accesses = 0,
> If we're gonna set above two fields anyway later, we could simply remove above
> three lines.
>
>> +		/* no matter its age */
>> +		.min_age_region = 0,
>> +		.max_age_region = UINT_MAX,
>> +	};
>>   	struct damos_quota quota = damon_lru_sort_quota;
>>   
>>   	/* Use half of total quota for hot/cold pages sorting */
>>   	quota.ms = quota.ms / 2;
>>   
>> +	switch (action) {
>> +	case DAMOS_LRU_PRIO:
>> +		pattern.min_nr_accesses = thres;
>> +		pattern.max_nr_accesses = UINT_MAX;
>> +		break;
>> +	case DAMOS_LRU_DEPRIO:
>> +		pattern.min_age_region = thres;
>> +		break;
>> +	default:
>> +		return NULL;
>> +	}
>> +
> This switch-case makes me wondering if the 'default' case really possible case.
> I think it would be clearer to set these from caller.
>
> IMHO, it might be clearer and shorter to define a static global 'struct
> damos_access_pattern' stub variable, and make the
> damon_lru_sort_new_{hot,cold}_scheme() copies it to their local variable,
> update the relevant fields, and pass that to 'damon_new_scheme()'.  What do you
> think?
>
>>   	return damon_new_scheme(
>>   			/* find the pattern, and */
>> -			pattern,
>> +			&pattern,
>>   			/* (de)prioritize on LRU-lists */
>>   			action,
>>   			/* under the quota. */
>> @@ -157,37 +180,13 @@ static struct damos *damon_lru_sort_new_scheme(
>>   /* Create a DAMON-based operation scheme for hot memory regions */
>>   static struct damos *damon_lru_sort_new_hot_scheme(unsigned int hot_thres)
>>   {
>> -	struct damos_access_pattern pattern = {
>> -		/* Find regions having PAGE_SIZE or larger size */
>> -		.min_sz_region = PAGE_SIZE,
>> -		.max_sz_region = ULONG_MAX,
>> -		/* and accessed for more than the threshold */
>> -		.min_nr_accesses = hot_thres,
>> -		.max_nr_accesses = UINT_MAX,
>> -		/* no matter its age */
>> -		.min_age_region = 0,
>> -		.max_age_region = UINT_MAX,
>> -	};
>> -
>> -	return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_PRIO);
>> +	return damon_lru_sort_new_scheme(hot_thres, DAMOS_LRU_PRIO);
> If we follow what I suggested above, we could make this like below:
>
> 	struct damos_access_pattern pattern = damon_lru_sort_stub_access_pattern;
>
> 	pattern.min_nr_accesses = hot_thres;
> 	return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_PRIO);
Agree totally,  i will fix it in the next patch.
>>   }
>>   
>>   /* Create a DAMON-based operation scheme for cold memory regions */
>>   static struct damos *damon_lru_sort_new_cold_scheme(unsigned int cold_thres)
>>   {
>> -	struct damos_access_pattern pattern = {
>> -		/* Find regions having PAGE_SIZE or larger size */
>> -		.min_sz_region = PAGE_SIZE,
>> -		.max_sz_region = ULONG_MAX,
>> -		/* and not accessed at all */
>> -		.min_nr_accesses = 0,
>> -		.max_nr_accesses = 0,
>> -		/* for min_age or more micro-seconds */
>> -		.min_age_region = cold_thres,
>> -		.max_age_region = UINT_MAX,
>> -	};
>> -
>> -	return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_DEPRIO);
>> +	return damon_lru_sort_new_scheme(cold_thres, DAMOS_LRU_DEPRIO);
> And similarly here.
>
>>   }
>>   
>>   static int damon_lru_sort_apply_parameters(void)
>> -- 
>> 2.31.0
>>
>>
>
> Thanks,
> SJ