[PATCH -mm] mm, swap: Use page-cluster as max window of VMA based swap readahead

[PATCH -mm] mm, swap: Use page-cluster as max window of VMA based swap readahead

[Huang, Ying]

From: Huang Ying <ying.huang@intel.com>

When the VMA based swap readahead was introduced, a new knob

  /sys/kernel/mm/swap/vma_ra_max_order

was added as the max window of VMA swap readahead.  This is to make it
possible to use different max window for VMA based readahead and
original physical readahead.  But Minchan Kim pointed out that this
will cause a regression because setting page-cluster sysctl to zero
cannot disable swap readahead with the change.

To fix the regression, the page-cluster sysctl is used as the max
window of both the VMA based swap readahead and original physical swap
readahead.  If more fine grained control is needed in the future, more
knobs can be added as the subordinate knobs of the page-cluster
sysctl.

The vma_ra_max_order knob is deleted.  Because the knob was
introduced in v4.14-rc1, and this patch is targeting being merged
before v4.14 releasing, there should be no existing users of this
newly added ABI.

Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Reported-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
---
 Documentation/ABI/testing/sysfs-kernel-mm-swap | 10 ---------
 mm/swap_state.c                                | 31 ++------------------------
 2 files changed, 2 insertions(+), 39 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-swap b/Documentation/ABI/testing/sysfs-kernel-mm-swap
index 587db52084c7..94672016c268 100644
--- a/Documentation/ABI/testing/sysfs-kernel-mm-swap
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-swap
@@ -14,13 +14,3 @@ Description:	Enable/disable VMA based swap readahead.
 		still used for tmpfs etc. other users.  If set to
 		false, the global swap readahead algorithm will be
 		used for all swappable pages.
-
-What:		/sys/kernel/mm/swap/vma_ra_max_order
-Date:		August 2017
-Contact:	Linux memory management mailing list <linux-mm@kvack.org>
-Description:	The max readahead size in order for VMA based swap readahead
-
-		VMA based swap readahead algorithm will readahead at
-		most 1 << max_order pages for each readahead.  The
-		real readahead size for each readahead will be scaled
-		according to the estimation algorithm.
diff --git a/mm/swap_state.c b/mm/swap_state.c
index ed91091d1e68..4d01ecff62d9 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -39,10 +39,6 @@ struct address_space *swapper_spaces[MAX_SWAPFILES];
 static unsigned int nr_swapper_spaces[MAX_SWAPFILES];
 bool swap_vma_readahead = true;
 
-#define SWAP_RA_MAX_ORDER_DEFAULT	3
-
-static int swap_ra_max_order = SWAP_RA_MAX_ORDER_DEFAULT;
-
 #define SWAP_RA_WIN_SHIFT	(PAGE_SHIFT / 2)
 #define SWAP_RA_HITS_MASK	((1UL << SWAP_RA_WIN_SHIFT) - 1)
 #define SWAP_RA_HITS_MAX	SWAP_RA_HITS_MASK
@@ -672,7 +668,8 @@ struct page *swap_readahead_detect(struct vm_fault *vmf,
 	if (page)
 		return page;
 
-	max_win = 1 << READ_ONCE(swap_ra_max_order);
+	max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
+			     SWAP_RA_ORDER_CEILING);
 	if (max_win == 1) {
 		swap_ra->win = 1;
 		return NULL;
@@ -786,32 +783,8 @@ static struct kobj_attribute vma_ra_enabled_attr =
 	__ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show,
 	       vma_ra_enabled_store);
 
-static ssize_t vma_ra_max_order_show(struct kobject *kobj,
-				     struct kobj_attribute *attr, char *buf)
-{
-	return sprintf(buf, "%d\n", swap_ra_max_order);
-}
-static ssize_t vma_ra_max_order_store(struct kobject *kobj,
-				      struct kobj_attribute *attr,
-				      const char *buf, size_t count)
-{
-	int err, v;
-
-	err = kstrtoint(buf, 10, &v);
-	if (err || v > SWAP_RA_ORDER_CEILING || v <= 0)
-		return -EINVAL;
-
-	swap_ra_max_order = v;
-
-	return count;
-}
-static struct kobj_attribute vma_ra_max_order_attr =
-	__ATTR(vma_ra_max_order, 0644, vma_ra_max_order_show,
-	       vma_ra_max_order_store);
-
 static struct attribute *swap_attrs[] = {
 	&vma_ra_enabled_attr.attr,
-	&vma_ra_max_order_attr.attr,
 	NULL,
 };
 
-- 
2.14.2

[PATCH -mm] mm, swap: Use page-cluster as max window of VMA based swap readahead

[Huang, Ying]

From: Huang Ying <ying.huang@intel.com>

When the VMA based swap readahead was introduced, a new knob

  /sys/kernel/mm/swap/vma_ra_max_order

was added as the max window of VMA swap readahead.  This is to make it
possible to use different max window for VMA based readahead and
original physical readahead.  But Minchan Kim pointed out that this
will cause a regression because setting page-cluster sysctl to zero
cannot disable swap readahead with the change.

To fix the regression, the page-cluster sysctl is used as the max
window of both the VMA based swap readahead and original physical swap
readahead.  If more fine grained control is needed in the future, more
knobs can be added as the subordinate knobs of the page-cluster
sysctl.

The vma_ra_max_order knob is deleted.  Because the knob was
introduced in v4.14-rc1, and this patch is targeting being merged
before v4.14 releasing, there should be no existing users of this
newly added ABI.

Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Reported-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
---
 Documentation/ABI/testing/sysfs-kernel-mm-swap | 10 ---------
 mm/swap_state.c                                | 31 ++------------------------
 2 files changed, 2 insertions(+), 39 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-swap b/Documentation/ABI/testing/sysfs-kernel-mm-swap
index 587db52084c7..94672016c268 100644
--- a/Documentation/ABI/testing/sysfs-kernel-mm-swap
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-swap
@@ -14,13 +14,3 @@ Description:	Enable/disable VMA based swap readahead.
 		still used for tmpfs etc. other users.  If set to
 		false, the global swap readahead algorithm will be
 		used for all swappable pages.
-
-What:		/sys/kernel/mm/swap/vma_ra_max_order
-Date:		August 2017
-Contact:	Linux memory management mailing list <linux-mm@kvack.org>
-Description:	The max readahead size in order for VMA based swap readahead
-
-		VMA based swap readahead algorithm will readahead at
-		most 1 << max_order pages for each readahead.  The
-		real readahead size for each readahead will be scaled
-		according to the estimation algorithm.
diff --git a/mm/swap_state.c b/mm/swap_state.c
index ed91091d1e68..4d01ecff62d9 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -39,10 +39,6 @@ struct address_space *swapper_spaces[MAX_SWAPFILES];
 static unsigned int nr_swapper_spaces[MAX_SWAPFILES];
 bool swap_vma_readahead = true;
 
-#define SWAP_RA_MAX_ORDER_DEFAULT	3
-
-static int swap_ra_max_order = SWAP_RA_MAX_ORDER_DEFAULT;
-
 #define SWAP_RA_WIN_SHIFT	(PAGE_SHIFT / 2)
 #define SWAP_RA_HITS_MASK	((1UL << SWAP_RA_WIN_SHIFT) - 1)
 #define SWAP_RA_HITS_MAX	SWAP_RA_HITS_MASK
@@ -672,7 +668,8 @@ struct page *swap_readahead_detect(struct vm_fault *vmf,
 	if (page)
 		return page;
 
-	max_win = 1 << READ_ONCE(swap_ra_max_order);
+	max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
+			     SWAP_RA_ORDER_CEILING);
 	if (max_win == 1) {
 		swap_ra->win = 1;
 		return NULL;
@@ -786,32 +783,8 @@ static struct kobj_attribute vma_ra_enabled_attr =
 	__ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show,
 	       vma_ra_enabled_store);
 
-static ssize_t vma_ra_max_order_show(struct kobject *kobj,
-				     struct kobj_attribute *attr, char *buf)
-{
-	return sprintf(buf, "%d\n", swap_ra_max_order);
-}
-static ssize_t vma_ra_max_order_store(struct kobject *kobj,
-				      struct kobj_attribute *attr,
-				      const char *buf, size_t count)
-{
-	int err, v;
-
-	err = kstrtoint(buf, 10, &v);
-	if (err || v > SWAP_RA_ORDER_CEILING || v <= 0)
-		return -EINVAL;
-
-	swap_ra_max_order = v;
-
-	return count;
-}
-static struct kobj_attribute vma_ra_max_order_attr =
-	__ATTR(vma_ra_max_order, 0644, vma_ra_max_order_show,
-	       vma_ra_max_order_store);
-
 static struct attribute *swap_attrs[] = {
 	&vma_ra_enabled_attr.attr,
-	&vma_ra_max_order_attr.attr,
 	NULL,
 };
 
-- 
2.14.2

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Re: [PATCH -mm] mm, swap: Use page-cluster as max window of VMA based swap readahead

[Minchan Kim]

On Tue, Oct 10, 2017 at 02:08:55PM +0800, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
> 
> When the VMA based swap readahead was introduced, a new knob
> 
>   /sys/kernel/mm/swap/vma_ra_max_order
> 
> was added as the max window of VMA swap readahead.  This is to make it
> possible to use different max window for VMA based readahead and
> original physical readahead.  But Minchan Kim pointed out that this
> will cause a regression because setting page-cluster sysctl to zero
> cannot disable swap readahead with the change.
> 
> To fix the regression, the page-cluster sysctl is used as the max
> window of both the VMA based swap readahead and original physical swap
> readahead.  If more fine grained control is needed in the future, more
> knobs can be added as the subordinate knobs of the page-cluster
> sysctl.
> 
> The vma_ra_max_order knob is deleted.  Because the knob was
> introduced in v4.14-rc1, and this patch is targeting being merged
> before v4.14 releasing, there should be no existing users of this
> newly added ABI.
> 
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Shaohua Li <shli@kernel.org>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Fengguang Wu <fengguang.wu@intel.com>
> Cc: Tim Chen <tim.c.chen@intel.com>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Reported-by: Minchan Kim <minchan@kernel.org>

It seems your script is Ccing only with Cc: tag, not other tags.
Fix it so any participant of topic can get the mail.

> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> ---
>  Documentation/ABI/testing/sysfs-kernel-mm-swap | 10 ---------
>  mm/swap_state.c                                | 31 ++------------------------
>  2 files changed, 2 insertions(+), 39 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-swap b/Documentation/ABI/testing/sysfs-kernel-mm-swap
> index 587db52084c7..94672016c268 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-mm-swap
> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-swap
> @@ -14,13 +14,3 @@ Description:	Enable/disable VMA based swap readahead.
>  		still used for tmpfs etc. other users.  If set to
>  		false, the global swap readahead algorithm will be
>  		used for all swappable pages.
> -
> -What:		/sys/kernel/mm/swap/vma_ra_max_order
> -Date:		August 2017
> -Contact:	Linux memory management mailing list <linux-mm@kvack.org>
> -Description:	The max readahead size in order for VMA based swap readahead
> -
> -		VMA based swap readahead algorithm will readahead at
> -		most 1 << max_order pages for each readahead.  The
> -		real readahead size for each readahead will be scaled
> -		according to the estimation algorithm.
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index ed91091d1e68..4d01ecff62d9 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -39,10 +39,6 @@ struct address_space *swapper_spaces[MAX_SWAPFILES];
>  static unsigned int nr_swapper_spaces[MAX_SWAPFILES];
>  bool swap_vma_readahead = true;
>  
> -#define SWAP_RA_MAX_ORDER_DEFAULT	3
> -
> -static int swap_ra_max_order = SWAP_RA_MAX_ORDER_DEFAULT;
> -
>  #define SWAP_RA_WIN_SHIFT	(PAGE_SHIFT / 2)
>  #define SWAP_RA_HITS_MASK	((1UL << SWAP_RA_WIN_SHIFT) - 1)
>  #define SWAP_RA_HITS_MAX	SWAP_RA_HITS_MASK
> @@ -672,7 +668,8 @@ struct page *swap_readahead_detect(struct vm_fault *vmf,
>  	if (page)
>  		return page;
>  
> -	max_win = 1 << READ_ONCE(swap_ra_max_order);
> +	max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
> +			     SWAP_RA_ORDER_CEILING);


Why doesn't you check it in swap_use_vma_readahead in my original patch?
My purpose in there is to avoid unnecessary function call and
lookup_swap_cache in there.
If you really want to do that in swap_readahead_detect itself, please
move above routine to ahead of faddr = vmf->address to avoid unncessary
instructions.

Re: [PATCH -mm] mm, swap: Use page-cluster as max window of VMA based swap readahead

[Minchan Kim]

On Tue, Oct 10, 2017 at 02:08:55PM +0800, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
> 
> When the VMA based swap readahead was introduced, a new knob
> 
>   /sys/kernel/mm/swap/vma_ra_max_order
> 
> was added as the max window of VMA swap readahead.  This is to make it
> possible to use different max window for VMA based readahead and
> original physical readahead.  But Minchan Kim pointed out that this
> will cause a regression because setting page-cluster sysctl to zero
> cannot disable swap readahead with the change.
> 
> To fix the regression, the page-cluster sysctl is used as the max
> window of both the VMA based swap readahead and original physical swap
> readahead.  If more fine grained control is needed in the future, more
> knobs can be added as the subordinate knobs of the page-cluster
> sysctl.
> 
> The vma_ra_max_order knob is deleted.  Because the knob was
> introduced in v4.14-rc1, and this patch is targeting being merged
> before v4.14 releasing, there should be no existing users of this
> newly added ABI.
> 
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Shaohua Li <shli@kernel.org>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Fengguang Wu <fengguang.wu@intel.com>
> Cc: Tim Chen <tim.c.chen@intel.com>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Reported-by: Minchan Kim <minchan@kernel.org>

It seems your script is Ccing only with Cc: tag, not other tags.
Fix it so any participant of topic can get the mail.

> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> ---
>  Documentation/ABI/testing/sysfs-kernel-mm-swap | 10 ---------
>  mm/swap_state.c                                | 31 ++------------------------
>  2 files changed, 2 insertions(+), 39 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-swap b/Documentation/ABI/testing/sysfs-kernel-mm-swap
> index 587db52084c7..94672016c268 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-mm-swap
> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-swap
> @@ -14,13 +14,3 @@ Description:	Enable/disable VMA based swap readahead.
>  		still used for tmpfs etc. other users.  If set to
>  		false, the global swap readahead algorithm will be
>  		used for all swappable pages.
> -
> -What:		/sys/kernel/mm/swap/vma_ra_max_order
> -Date:		August 2017
> -Contact:	Linux memory management mailing list <linux-mm@kvack.org>
> -Description:	The max readahead size in order for VMA based swap readahead
> -
> -		VMA based swap readahead algorithm will readahead at
> -		most 1 << max_order pages for each readahead.  The
> -		real readahead size for each readahead will be scaled
> -		according to the estimation algorithm.
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index ed91091d1e68..4d01ecff62d9 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -39,10 +39,6 @@ struct address_space *swapper_spaces[MAX_SWAPFILES];
>  static unsigned int nr_swapper_spaces[MAX_SWAPFILES];
>  bool swap_vma_readahead = true;
>  
> -#define SWAP_RA_MAX_ORDER_DEFAULT	3
> -
> -static int swap_ra_max_order = SWAP_RA_MAX_ORDER_DEFAULT;
> -
>  #define SWAP_RA_WIN_SHIFT	(PAGE_SHIFT / 2)
>  #define SWAP_RA_HITS_MASK	((1UL << SWAP_RA_WIN_SHIFT) - 1)
>  #define SWAP_RA_HITS_MAX	SWAP_RA_HITS_MASK
> @@ -672,7 +668,8 @@ struct page *swap_readahead_detect(struct vm_fault *vmf,
>  	if (page)
>  		return page;
>  
> -	max_win = 1 << READ_ONCE(swap_ra_max_order);
> +	max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
> +			     SWAP_RA_ORDER_CEILING);


Why doesn't you check it in swap_use_vma_readahead in my original patch?
My purpose in there is to avoid unnecessary function call and
lookup_swap_cache in there.
If you really want to do that in swap_readahead_detect itself, please
move above routine to ahead of faddr = vmf->address to avoid unncessary
instructions.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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Re: [PATCH -mm] mm, swap: Use page-cluster as max window of VMA based swap readahead

[Huang, Ying]

Minchan Kim <minchan@kernel.org> writes:

> On Tue, Oct 10, 2017 at 02:08:55PM +0800, Huang, Ying wrote:
>> From: Huang Ying <ying.huang@intel.com>
>> 
>> When the VMA based swap readahead was introduced, a new knob
>> 
>>   /sys/kernel/mm/swap/vma_ra_max_order
>> 
>> was added as the max window of VMA swap readahead.  This is to make it
>> possible to use different max window for VMA based readahead and
>> original physical readahead.  But Minchan Kim pointed out that this
>> will cause a regression because setting page-cluster sysctl to zero
>> cannot disable swap readahead with the change.
>> 
>> To fix the regression, the page-cluster sysctl is used as the max
>> window of both the VMA based swap readahead and original physical swap
>> readahead.  If more fine grained control is needed in the future, more
>> knobs can be added as the subordinate knobs of the page-cluster
>> sysctl.
>> 
>> The vma_ra_max_order knob is deleted.  Because the knob was
>> introduced in v4.14-rc1, and this patch is targeting being merged
>> before v4.14 releasing, there should be no existing users of this
>> newly added ABI.
>> 
>> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> Cc: Rik van Riel <riel@redhat.com>
>> Cc: Shaohua Li <shli@kernel.org>
>> Cc: Hugh Dickins <hughd@google.com>
>> Cc: Fengguang Wu <fengguang.wu@intel.com>
>> Cc: Tim Chen <tim.c.chen@intel.com>
>> Cc: Dave Hansen <dave.hansen@intel.com>
>> Reported-by: Minchan Kim <minchan@kernel.org>
>
> It seems your script is Ccing only with Cc: tag, not other tags.
> Fix it so any participant of topic can get the mail.

I just used `git send-email`, no other scripts.  We need to fix `git send-email`?

>> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>> ---
>>  Documentation/ABI/testing/sysfs-kernel-mm-swap | 10 ---------
>>  mm/swap_state.c                                | 31 ++------------------------
>>  2 files changed, 2 insertions(+), 39 deletions(-)
>> 
>> diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-swap b/Documentation/ABI/testing/sysfs-kernel-mm-swap
>> index 587db52084c7..94672016c268 100644
>> --- a/Documentation/ABI/testing/sysfs-kernel-mm-swap
>> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-swap
>> @@ -14,13 +14,3 @@ Description:	Enable/disable VMA based swap readahead.
>>  		still used for tmpfs etc. other users.  If set to
>>  		false, the global swap readahead algorithm will be
>>  		used for all swappable pages.
>> -
>> -What:		/sys/kernel/mm/swap/vma_ra_max_order
>> -Date:		August 2017
>> -Contact:	Linux memory management mailing list <linux-mm@kvack.org>
>> -Description:	The max readahead size in order for VMA based swap readahead
>> -
>> -		VMA based swap readahead algorithm will readahead at
>> -		most 1 << max_order pages for each readahead.  The
>> -		real readahead size for each readahead will be scaled
>> -		according to the estimation algorithm.
>> diff --git a/mm/swap_state.c b/mm/swap_state.c
>> index ed91091d1e68..4d01ecff62d9 100644
>> --- a/mm/swap_state.c
>> +++ b/mm/swap_state.c
>> @@ -39,10 +39,6 @@ struct address_space *swapper_spaces[MAX_SWAPFILES];
>>  static unsigned int nr_swapper_spaces[MAX_SWAPFILES];
>>  bool swap_vma_readahead = true;
>>  
>> -#define SWAP_RA_MAX_ORDER_DEFAULT	3
>> -
>> -static int swap_ra_max_order = SWAP_RA_MAX_ORDER_DEFAULT;
>> -
>>  #define SWAP_RA_WIN_SHIFT	(PAGE_SHIFT / 2)
>>  #define SWAP_RA_HITS_MASK	((1UL << SWAP_RA_WIN_SHIFT) - 1)
>>  #define SWAP_RA_HITS_MAX	SWAP_RA_HITS_MASK
>> @@ -672,7 +668,8 @@ struct page *swap_readahead_detect(struct vm_fault *vmf,
>>  	if (page)
>>  		return page;
>>  
>> -	max_win = 1 << READ_ONCE(swap_ra_max_order);
>> +	max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
>> +			     SWAP_RA_ORDER_CEILING);
>
>
> Why doesn't you check it in swap_use_vma_readahead in my original patch?
> My purpose in there is to avoid unnecessary function call and
> lookup_swap_cache in there.
> If you really want to do that in swap_readahead_detect itself, please
> move above routine to ahead of faddr = vmf->address to avoid unncessary
> instructions.

Although the avoided instructions is just a few, I can move the max
window checking as the first statements in the function.

Best Regards,
Huang, Ying

Re: [PATCH -mm] mm, swap: Use page-cluster as max window of VMA based swap readahead

[Huang, Ying]

Minchan Kim <minchan@kernel.org> writes:

> On Tue, Oct 10, 2017 at 02:08:55PM +0800, Huang, Ying wrote:
>> From: Huang Ying <ying.huang@intel.com>
>> 
>> When the VMA based swap readahead was introduced, a new knob
>> 
>>   /sys/kernel/mm/swap/vma_ra_max_order
>> 
>> was added as the max window of VMA swap readahead.  This is to make it
>> possible to use different max window for VMA based readahead and
>> original physical readahead.  But Minchan Kim pointed out that this
>> will cause a regression because setting page-cluster sysctl to zero
>> cannot disable swap readahead with the change.
>> 
>> To fix the regression, the page-cluster sysctl is used as the max
>> window of both the VMA based swap readahead and original physical swap
>> readahead.  If more fine grained control is needed in the future, more
>> knobs can be added as the subordinate knobs of the page-cluster
>> sysctl.
>> 
>> The vma_ra_max_order knob is deleted.  Because the knob was
>> introduced in v4.14-rc1, and this patch is targeting being merged
>> before v4.14 releasing, there should be no existing users of this
>> newly added ABI.
>> 
>> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> Cc: Rik van Riel <riel@redhat.com>
>> Cc: Shaohua Li <shli@kernel.org>
>> Cc: Hugh Dickins <hughd@google.com>
>> Cc: Fengguang Wu <fengguang.wu@intel.com>
>> Cc: Tim Chen <tim.c.chen@intel.com>
>> Cc: Dave Hansen <dave.hansen@intel.com>
>> Reported-by: Minchan Kim <minchan@kernel.org>
>
> It seems your script is Ccing only with Cc: tag, not other tags.
> Fix it so any participant of topic can get the mail.

I just used `git send-email`, no other scripts.  We need to fix `git send-email`?

>> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>> ---
>>  Documentation/ABI/testing/sysfs-kernel-mm-swap | 10 ---------
>>  mm/swap_state.c                                | 31 ++------------------------
>>  2 files changed, 2 insertions(+), 39 deletions(-)
>> 
>> diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-swap b/Documentation/ABI/testing/sysfs-kernel-mm-swap
>> index 587db52084c7..94672016c268 100644
>> --- a/Documentation/ABI/testing/sysfs-kernel-mm-swap
>> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-swap
>> @@ -14,13 +14,3 @@ Description:	Enable/disable VMA based swap readahead.
>>  		still used for tmpfs etc. other users.  If set to
>>  		false, the global swap readahead algorithm will be
>>  		used for all swappable pages.
>> -
>> -What:		/sys/kernel/mm/swap/vma_ra_max_order
>> -Date:		August 2017
>> -Contact:	Linux memory management mailing list <linux-mm@kvack.org>
>> -Description:	The max readahead size in order for VMA based swap readahead
>> -
>> -		VMA based swap readahead algorithm will readahead at
>> -		most 1 << max_order pages for each readahead.  The
>> -		real readahead size for each readahead will be scaled
>> -		according to the estimation algorithm.
>> diff --git a/mm/swap_state.c b/mm/swap_state.c
>> index ed91091d1e68..4d01ecff62d9 100644
>> --- a/mm/swap_state.c
>> +++ b/mm/swap_state.c
>> @@ -39,10 +39,6 @@ struct address_space *swapper_spaces[MAX_SWAPFILES];
>>  static unsigned int nr_swapper_spaces[MAX_SWAPFILES];
>>  bool swap_vma_readahead = true;
>>  
>> -#define SWAP_RA_MAX_ORDER_DEFAULT	3
>> -
>> -static int swap_ra_max_order = SWAP_RA_MAX_ORDER_DEFAULT;
>> -
>>  #define SWAP_RA_WIN_SHIFT	(PAGE_SHIFT / 2)
>>  #define SWAP_RA_HITS_MASK	((1UL << SWAP_RA_WIN_SHIFT) - 1)
>>  #define SWAP_RA_HITS_MAX	SWAP_RA_HITS_MASK
>> @@ -672,7 +668,8 @@ struct page *swap_readahead_detect(struct vm_fault *vmf,
>>  	if (page)
>>  		return page;
>>  
>> -	max_win = 1 << READ_ONCE(swap_ra_max_order);
>> +	max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
>> +			     SWAP_RA_ORDER_CEILING);
>
>
> Why doesn't you check it in swap_use_vma_readahead in my original patch?
> My purpose in there is to avoid unnecessary function call and
> lookup_swap_cache in there.
> If you really want to do that in swap_readahead_detect itself, please
> move above routine to ahead of faddr = vmf->address to avoid unncessary
> instructions.

Although the avoided instructions is just a few, I can move the max
window checking as the first statements in the function.

Best Regards,
Huang, Ying

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Re: [PATCH -mm] mm, swap: Use page-cluster as max window of VMA based swap readahead

[Minchan Kim]

On Tue, Oct 10, 2017 at 04:50:10PM +0800, Huang, Ying wrote:
> Minchan Kim <minchan@kernel.org> writes:
> 
> > On Tue, Oct 10, 2017 at 02:08:55PM +0800, Huang, Ying wrote:
> >> From: Huang Ying <ying.huang@intel.com>
> >> 
> >> When the VMA based swap readahead was introduced, a new knob
> >> 
> >>   /sys/kernel/mm/swap/vma_ra_max_order
> >> 
> >> was added as the max window of VMA swap readahead.  This is to make it
> >> possible to use different max window for VMA based readahead and
> >> original physical readahead.  But Minchan Kim pointed out that this
> >> will cause a regression because setting page-cluster sysctl to zero
> >> cannot disable swap readahead with the change.
> >> 
> >> To fix the regression, the page-cluster sysctl is used as the max
> >> window of both the VMA based swap readahead and original physical swap
> >> readahead.  If more fine grained control is needed in the future, more
> >> knobs can be added as the subordinate knobs of the page-cluster
> >> sysctl.
> >> 
> >> The vma_ra_max_order knob is deleted.  Because the knob was
> >> introduced in v4.14-rc1, and this patch is targeting being merged
> >> before v4.14 releasing, there should be no existing users of this
> >> newly added ABI.
> >> 
> >> Cc: Johannes Weiner <hannes@cmpxchg.org>
> >> Cc: Rik van Riel <riel@redhat.com>
> >> Cc: Shaohua Li <shli@kernel.org>
> >> Cc: Hugh Dickins <hughd@google.com>
> >> Cc: Fengguang Wu <fengguang.wu@intel.com>
> >> Cc: Tim Chen <tim.c.chen@intel.com>
> >> Cc: Dave Hansen <dave.hansen@intel.com>
> >> Reported-by: Minchan Kim <minchan@kernel.org>
> >
> > It seems your script is Ccing only with Cc: tag, not other tags.
> > Fix it so any participant of topic can get the mail.
> 
> I just used `git send-email`, no other scripts.  We need to fix `git send-email`?

You can do it via cccmd.

Just a reference:

~/bin/kcccmd
sed -nre 's/^(Acked|Reviewed|Reported|Tested|Suggested)-by: //p' "$1"

Re: [PATCH -mm] mm, swap: Use page-cluster as max window of VMA based swap readahead

[Minchan Kim]

On Tue, Oct 10, 2017 at 04:50:10PM +0800, Huang, Ying wrote:
> Minchan Kim <minchan@kernel.org> writes:
> 
> > On Tue, Oct 10, 2017 at 02:08:55PM +0800, Huang, Ying wrote:
> >> From: Huang Ying <ying.huang@intel.com>
> >> 
> >> When the VMA based swap readahead was introduced, a new knob
> >> 
> >>   /sys/kernel/mm/swap/vma_ra_max_order
> >> 
> >> was added as the max window of VMA swap readahead.  This is to make it
> >> possible to use different max window for VMA based readahead and
> >> original physical readahead.  But Minchan Kim pointed out that this
> >> will cause a regression because setting page-cluster sysctl to zero
> >> cannot disable swap readahead with the change.
> >> 
> >> To fix the regression, the page-cluster sysctl is used as the max
> >> window of both the VMA based swap readahead and original physical swap
> >> readahead.  If more fine grained control is needed in the future, more
> >> knobs can be added as the subordinate knobs of the page-cluster
> >> sysctl.
> >> 
> >> The vma_ra_max_order knob is deleted.  Because the knob was
> >> introduced in v4.14-rc1, and this patch is targeting being merged
> >> before v4.14 releasing, there should be no existing users of this
> >> newly added ABI.
> >> 
> >> Cc: Johannes Weiner <hannes@cmpxchg.org>
> >> Cc: Rik van Riel <riel@redhat.com>
> >> Cc: Shaohua Li <shli@kernel.org>
> >> Cc: Hugh Dickins <hughd@google.com>
> >> Cc: Fengguang Wu <fengguang.wu@intel.com>
> >> Cc: Tim Chen <tim.c.chen@intel.com>
> >> Cc: Dave Hansen <dave.hansen@intel.com>
> >> Reported-by: Minchan Kim <minchan@kernel.org>
> >
> > It seems your script is Ccing only with Cc: tag, not other tags.
> > Fix it so any participant of topic can get the mail.
> 
> I just used `git send-email`, no other scripts.  We need to fix `git send-email`?

You can do it via cccmd.

Just a reference:

~/bin/kcccmd
sed -nre 's/^(Acked|Reviewed|Reported|Tested|Suggested)-by: //p' "$1"

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH -mm] mm, swap: Use page-cluster as max window of VMA based swap readahead

[Huang, Ying]

Minchan Kim <minchan@kernel.org> writes:

> On Tue, Oct 10, 2017 at 04:50:10PM +0800, Huang, Ying wrote:
>> Minchan Kim <minchan@kernel.org> writes:
>> 
>> > On Tue, Oct 10, 2017 at 02:08:55PM +0800, Huang, Ying wrote:
>> >> From: Huang Ying <ying.huang@intel.com>
>> >> 
>> >> When the VMA based swap readahead was introduced, a new knob
>> >> 
>> >>   /sys/kernel/mm/swap/vma_ra_max_order
>> >> 
>> >> was added as the max window of VMA swap readahead.  This is to make it
>> >> possible to use different max window for VMA based readahead and
>> >> original physical readahead.  But Minchan Kim pointed out that this
>> >> will cause a regression because setting page-cluster sysctl to zero
>> >> cannot disable swap readahead with the change.
>> >> 
>> >> To fix the regression, the page-cluster sysctl is used as the max
>> >> window of both the VMA based swap readahead and original physical swap
>> >> readahead.  If more fine grained control is needed in the future, more
>> >> knobs can be added as the subordinate knobs of the page-cluster
>> >> sysctl.
>> >> 
>> >> The vma_ra_max_order knob is deleted.  Because the knob was
>> >> introduced in v4.14-rc1, and this patch is targeting being merged
>> >> before v4.14 releasing, there should be no existing users of this
>> >> newly added ABI.
>> >> 
>> >> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> >> Cc: Rik van Riel <riel@redhat.com>
>> >> Cc: Shaohua Li <shli@kernel.org>
>> >> Cc: Hugh Dickins <hughd@google.com>
>> >> Cc: Fengguang Wu <fengguang.wu@intel.com>
>> >> Cc: Tim Chen <tim.c.chen@intel.com>
>> >> Cc: Dave Hansen <dave.hansen@intel.com>
>> >> Reported-by: Minchan Kim <minchan@kernel.org>
>> >
>> > It seems your script is Ccing only with Cc: tag, not other tags.
>> > Fix it so any participant of topic can get the mail.
>> 
>> I just used `git send-email`, no other scripts.  We need to fix `git send-email`?
>
> You can do it via cccmd.
>
> Just a reference:
>
> ~/bin/kcccmd
> sed -nre 's/^(Acked|Reviewed|Reported|Tested|Suggested)-by: //p' "$1"

Thanks, will use this script in the future.

Best Regards,
Huang, Ying

Re: [PATCH -mm] mm, swap: Use page-cluster as max window of VMA based swap readahead

[Huang, Ying]

Minchan Kim <minchan@kernel.org> writes:

> On Tue, Oct 10, 2017 at 04:50:10PM +0800, Huang, Ying wrote:
>> Minchan Kim <minchan@kernel.org> writes:
>> 
>> > On Tue, Oct 10, 2017 at 02:08:55PM +0800, Huang, Ying wrote:
>> >> From: Huang Ying <ying.huang@intel.com>
>> >> 
>> >> When the VMA based swap readahead was introduced, a new knob
>> >> 
>> >>   /sys/kernel/mm/swap/vma_ra_max_order
>> >> 
>> >> was added as the max window of VMA swap readahead.  This is to make it
>> >> possible to use different max window for VMA based readahead and
>> >> original physical readahead.  But Minchan Kim pointed out that this
>> >> will cause a regression because setting page-cluster sysctl to zero
>> >> cannot disable swap readahead with the change.
>> >> 
>> >> To fix the regression, the page-cluster sysctl is used as the max
>> >> window of both the VMA based swap readahead and original physical swap
>> >> readahead.  If more fine grained control is needed in the future, more
>> >> knobs can be added as the subordinate knobs of the page-cluster
>> >> sysctl.
>> >> 
>> >> The vma_ra_max_order knob is deleted.  Because the knob was
>> >> introduced in v4.14-rc1, and this patch is targeting being merged
>> >> before v4.14 releasing, there should be no existing users of this
>> >> newly added ABI.
>> >> 
>> >> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> >> Cc: Rik van Riel <riel@redhat.com>
>> >> Cc: Shaohua Li <shli@kernel.org>
>> >> Cc: Hugh Dickins <hughd@google.com>
>> >> Cc: Fengguang Wu <fengguang.wu@intel.com>
>> >> Cc: Tim Chen <tim.c.chen@intel.com>
>> >> Cc: Dave Hansen <dave.hansen@intel.com>
>> >> Reported-by: Minchan Kim <minchan@kernel.org>
>> >
>> > It seems your script is Ccing only with Cc: tag, not other tags.
>> > Fix it so any participant of topic can get the mail.
>> 
>> I just used `git send-email`, no other scripts.  We need to fix `git send-email`?
>
> You can do it via cccmd.
>
> Just a reference:
>
> ~/bin/kcccmd
> sed -nre 's/^(Acked|Reviewed|Reported|Tested|Suggested)-by: //p' "$1"

Thanks, will use this script in the future.

Best Regards,
Huang, Ying

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>