[PATCH v2 0/2] mm/damon: Simplify the damon regions access check

[PATCH v2 0/2] mm/damon: Simplify the damon regions access check

[xiakaixu1987]

From: Kaixu Xia <kaixuxia@tencent.com>

This patchset simplify the operations when checking the damon
regions accesses.

v2:
 -Update commit messages and fix the 80 characters warning.
 -Add the check when damon target changed.

Kaixu Xia (2):
  mm/damon: simplify the parameter passing for 'check_accesses'
  mm/damon/vaddr: remove comparison between mm and last_mm when checking
    region accesses

 mm/damon/paddr.c |  5 ++---
 mm/damon/vaddr.c | 13 +++++++------
 2 files changed, 9 insertions(+), 9 deletions(-)

-- 
2.27.0

[PATCH v2 1/2] mm/damon: simplify the parameter passing for 'check_accesses'

[xiakaixu1987]

From: Kaixu Xia <kaixuxia@tencent.com>

The parameter 'struct damon_ctx *ctx' isn't used in the functions
__damon_{p,v}a_check_access(), so we can remove it and simplify the
parameter passing.

Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
---
 mm/damon/paddr.c | 5 ++---
 mm/damon/vaddr.c | 6 +++---
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index dc131c6a5403..6b0d9e6aa677 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -166,8 +166,7 @@ static bool damon_pa_young(unsigned long paddr, unsigned long *page_sz)
 	return result.accessed;
 }
 
-static void __damon_pa_check_access(struct damon_ctx *ctx,
-				    struct damon_region *r)
+static void __damon_pa_check_access(struct damon_region *r)
 {
 	static unsigned long last_addr;
 	static unsigned long last_page_sz = PAGE_SIZE;
@@ -196,7 +195,7 @@ static unsigned int damon_pa_check_accesses(struct damon_ctx *ctx)
 
 	damon_for_each_target(t, ctx) {
 		damon_for_each_region(r, t) {
-			__damon_pa_check_access(ctx, r);
+			__damon_pa_check_access(r);
 			max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
 		}
 	}
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 3c7b9d6dca95..e481f81c3efb 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -532,8 +532,8 @@ static bool damon_va_young(struct mm_struct *mm, unsigned long addr,
  * mm	'mm_struct' for the given virtual address space
  * r	the region to be checked
  */
-static void __damon_va_check_access(struct damon_ctx *ctx,
-			       struct mm_struct *mm, struct damon_region *r)
+static void __damon_va_check_access(struct mm_struct *mm,
+				struct damon_region *r)
 {
 	static struct mm_struct *last_mm;
 	static unsigned long last_addr;
@@ -568,7 +568,7 @@ static unsigned int damon_va_check_accesses(struct damon_ctx *ctx)
 		if (!mm)
 			continue;
 		damon_for_each_region(r, t) {
-			__damon_va_check_access(ctx, mm, r);
+			__damon_va_check_access(mm, r);
 			max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
 		}
 		mmput(mm);
-- 
2.27.0

Re: [PATCH v2 1/2] mm/damon: simplify the parameter passing for 'check_accesses'

[SeongJae Park]

Hi Kaixu,

On Sat, 27 Aug 2022 17:02:50 +0800 xiakaixu1987@gmail.com wrote:

> From: Kaixu Xia <kaixuxia@tencent.com>
> 
> The parameter 'struct damon_ctx *ctx' isn't used in the functions
> __damon_{p,v}a_check_access(), so we can remove it and simplify the
> parameter passing.
> 
> Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>

Reviewed-by: SeongJae Park <sj@kernel.org>


Thanks,
SJ

> ---
>  mm/damon/paddr.c | 5 ++---
>  mm/damon/vaddr.c | 6 +++---
>  2 files changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
> index dc131c6a5403..6b0d9e6aa677 100644
> --- a/mm/damon/paddr.c
> +++ b/mm/damon/paddr.c
> @@ -166,8 +166,7 @@ static bool damon_pa_young(unsigned long paddr, unsigned long *page_sz)
>  	return result.accessed;
>  }
>  
> -static void __damon_pa_check_access(struct damon_ctx *ctx,
> -				    struct damon_region *r)
> +static void __damon_pa_check_access(struct damon_region *r)
>  {
>  	static unsigned long last_addr;
>  	static unsigned long last_page_sz = PAGE_SIZE;
> @@ -196,7 +195,7 @@ static unsigned int damon_pa_check_accesses(struct damon_ctx *ctx)
>  
>  	damon_for_each_target(t, ctx) {
>  		damon_for_each_region(r, t) {
> -			__damon_pa_check_access(ctx, r);
> +			__damon_pa_check_access(r);
>  			max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
>  		}
>  	}
> diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
> index 3c7b9d6dca95..e481f81c3efb 100644
> --- a/mm/damon/vaddr.c
> +++ b/mm/damon/vaddr.c
> @@ -532,8 +532,8 @@ static bool damon_va_young(struct mm_struct *mm, unsigned long addr,
>   * mm	'mm_struct' for the given virtual address space
>   * r	the region to be checked
>   */
> -static void __damon_va_check_access(struct damon_ctx *ctx,
> -			       struct mm_struct *mm, struct damon_region *r)
> +static void __damon_va_check_access(struct mm_struct *mm,
> +				struct damon_region *r)
>  {
>  	static struct mm_struct *last_mm;
>  	static unsigned long last_addr;
> @@ -568,7 +568,7 @@ static unsigned int damon_va_check_accesses(struct damon_ctx *ctx)
>  		if (!mm)
>  			continue;
>  		damon_for_each_region(r, t) {
> -			__damon_va_check_access(ctx, mm, r);
> +			__damon_va_check_access(mm, r);
>  			max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
>  		}
>  		mmput(mm);
> -- 
> 2.27.0

[PATCH v2 2/2] mm/damon/vaddr: remove comparison between mm and last_mm when checking region accesses

[xiakaixu1987]

From: Kaixu Xia <kaixuxia@tencent.com>

The damon regions that belong to the same damon target have the same
'struct mm_struct *mm', so it's unnecessary to compare the mm and last_mm
objects among the damon regions in one damon target when checking accesses.
But the check is necessary when the target changed in
'__damon_va_check_accesses()', so we can simplify the whole operation by
using the bool 'same_target' to indicate whether the target changed.

Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
---
 mm/damon/vaddr.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index e481f81c3efb..5f66c826ee3a 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -533,15 +533,14 @@ static bool damon_va_young(struct mm_struct *mm, unsigned long addr,
  * r	the region to be checked
  */
 static void __damon_va_check_access(struct mm_struct *mm,
-				struct damon_region *r)
+				struct damon_region *r, bool same_target)
 {
-	static struct mm_struct *last_mm;
 	static unsigned long last_addr;
 	static unsigned long last_page_sz = PAGE_SIZE;
 	static bool last_accessed;
 
 	/* If the region is in the last checked page, reuse the result */
-	if (mm == last_mm && (ALIGN_DOWN(last_addr, last_page_sz) ==
+	if (same_target && (ALIGN_DOWN(last_addr, last_page_sz) ==
 				ALIGN_DOWN(r->sampling_addr, last_page_sz))) {
 		if (last_accessed)
 			r->nr_accesses++;
@@ -552,7 +551,6 @@ static void __damon_va_check_access(struct mm_struct *mm,
 	if (last_accessed)
 		r->nr_accesses++;
 
-	last_mm = mm;
 	last_addr = r->sampling_addr;
 }
 
@@ -562,14 +560,17 @@ static unsigned int damon_va_check_accesses(struct damon_ctx *ctx)
 	struct mm_struct *mm;
 	struct damon_region *r;
 	unsigned int max_nr_accesses = 0;
+	bool same_target;
 
 	damon_for_each_target(t, ctx) {
 		mm = damon_get_mm(t);
 		if (!mm)
 			continue;
+		same_target = false;
 		damon_for_each_region(r, t) {
-			__damon_va_check_access(mm, r);
+			__damon_va_check_access(mm, r, same_target);
 			max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
+			same_target = true;
 		}
 		mmput(mm);
 	}
-- 
2.27.0

Re: [PATCH v2 2/2] mm/damon/vaddr: remove comparison between mm and last_mm when checking region accesses

[SeongJae Park]

Hi Kaixu,

> From: Kaixu Xia <kaixuxia@tencent.com>
> 
> The damon regions that belong to the same damon target have the same
> 'struct mm_struct *mm', so it's unnecessary to compare the mm and last_mm
> objects among the damon regions in one damon target when checking accesses.
> But the check is necessary when the target changed in
> '__damon_va_check_accesses()', so we can simplify the whole operation by
> using the bool 'same_target' to indicate whether the target changed.
> 
> Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>

Reviewed-by: SeongJae Park <sj@kernel.org>


Thanks,
SJ

> ---
>  mm/damon/vaddr.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
> index e481f81c3efb..5f66c826ee3a 100644
> --- a/mm/damon/vaddr.c
> +++ b/mm/damon/vaddr.c
> @@ -533,15 +533,14 @@ static bool damon_va_young(struct mm_struct *mm, unsigned long addr,
>   * r	the region to be checked
>   */
>  static void __damon_va_check_access(struct mm_struct *mm,
> -				struct damon_region *r)
> +				struct damon_region *r, bool same_target)
>  {
> -	static struct mm_struct *last_mm;
>  	static unsigned long last_addr;
>  	static unsigned long last_page_sz = PAGE_SIZE;
>  	static bool last_accessed;
>  
>  	/* If the region is in the last checked page, reuse the result */
> -	if (mm == last_mm && (ALIGN_DOWN(last_addr, last_page_sz) ==
> +	if (same_target && (ALIGN_DOWN(last_addr, last_page_sz) ==
>  				ALIGN_DOWN(r->sampling_addr, last_page_sz))) {
>  		if (last_accessed)
>  			r->nr_accesses++;
> @@ -552,7 +551,6 @@ static void __damon_va_check_access(struct mm_struct *mm,
>  	if (last_accessed)
>  		r->nr_accesses++;
>  
> -	last_mm = mm;
>  	last_addr = r->sampling_addr;
>  }
>  
> @@ -562,14 +560,17 @@ static unsigned int damon_va_check_accesses(struct damon_ctx *ctx)
>  	struct mm_struct *mm;
>  	struct damon_region *r;
>  	unsigned int max_nr_accesses = 0;
> +	bool same_target;
>  
>  	damon_for_each_target(t, ctx) {
>  		mm = damon_get_mm(t);
>  		if (!mm)
>  			continue;
> +		same_target = false;
>  		damon_for_each_region(r, t) {
> -			__damon_va_check_access(mm, r);
> +			__damon_va_check_access(mm, r, same_target);
>  			max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
> +			same_target = true;
>  		}
>  		mmput(mm);
>  	}
> -- 
> 2.27.0