[PATCH 1/2] memory tiering: read last_cpupid correctly in do_huge_pmd_numa_page()

[PATCH 1/2] memory tiering: read last_cpupid correctly in do_huge_pmd_numa_page()

[Zi Yan]

last_cpupid is only available when memory tiering is off or the folio
is in toptier node. Complete the check to read last_cpupid when it is
available.

Before the fix, the default last_cpupid will be used even if memory
tiering mode is turned off at runtime instead of the actual value. This
can prevent task_numa_fault() from getting right numa fault stats, but
should not cause any crash. User might see performance changes after the
fix.

Reported-by: David Hildenbrand <david@redhat.com>
Closes: https://lore.kernel.org/linux-mm/9af34a6b-ca56-4a64-8aa6-ade65f109288@redhat.com/
Fixes: 33024536bafd ("memory tiering: hot page selection with hint page fault latency")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
---
 mm/huge_memory.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f4be468e06a4..825317aee88e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1712,7 +1712,8 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 	 * For memory tiering mode, cpupid of slow memory page is used
 	 * to record page access time.  So use default value.
 	 */
-	if (node_is_toptier(nid))
+	if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) ||
+	    node_is_toptier(nid))
 		last_cpupid = folio_last_cpupid(folio);
 	target_nid = numa_migrate_prep(folio, vmf, haddr, nid, &flags);
 	if (target_nid == NUMA_NO_NODE)
-- 
2.43.0

[PATCH 2/2] memory tiering: introduce folio_has_cpupid() check

[Zi Yan]

Instead of open coded check for if memory tiering mode is on and a folio
is in the top tier memory, use a function to encapsulate the check.

Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
---
 include/linux/memory-tiers.h |  8 ++++++++
 kernel/sched/fair.c          |  3 +--
 mm/huge_memory.c             |  6 ++----
 mm/memory-tiers.c            | 17 +++++++++++++++++
 mm/memory.c                  |  3 +--
 mm/mprotect.c                |  3 +--
 6 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
index 0dc0cf2863e2..10c127d461c4 100644
--- a/include/linux/memory-tiers.h
+++ b/include/linux/memory-tiers.h
@@ -73,6 +73,10 @@ static inline bool node_is_toptier(int node)
 }
 #endif
 
+
+bool folio_has_cpupid(struct folio *folio);
+
+
 #else
 
 #define numa_demotion_enabled	false
@@ -151,5 +155,9 @@ static inline struct memory_dev_type *mt_find_alloc_memory_type(int adist,
 static inline void mt_put_memory_types(struct list_head *memory_types)
 {
 }
+static inline bool folio_has_cpupid(struct folio *folio)
+{
+	return true;
+}
 #endif	/* CONFIG_NUMA */
 #endif  /* _LINUX_MEMORY_TIERS_H */
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8a5b1ae0aa55..03de808cb3cc 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1840,8 +1840,7 @@ bool should_numa_migrate_memory(struct task_struct *p, struct folio *folio,
 	 * The pages in slow memory node should be migrated according
 	 * to hot/cold instead of private/shared.
 	 */
-	if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
-	    !node_is_toptier(src_nid)) {
+	if (!folio_has_cpupid(folio)) {
 		struct pglist_data *pgdat;
 		unsigned long rate_limit;
 		unsigned int latency, th, def_th;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 825317aee88e..d925a93bb9ed 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1712,8 +1712,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 	 * For memory tiering mode, cpupid of slow memory page is used
 	 * to record page access time.  So use default value.
 	 */
-	if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) ||
-	    node_is_toptier(nid))
+	if (folio_has_cpupid(folio))
 		last_cpupid = folio_last_cpupid(folio);
 	target_nid = numa_migrate_prep(folio, vmf, haddr, nid, &flags);
 	if (target_nid == NUMA_NO_NODE)
@@ -2066,8 +2065,7 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		    toptier)
 			goto unlock;
 
-		if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
-		    !toptier)
+		if (!folio_has_cpupid(folio))
 			folio_xchg_access_time(folio,
 					       jiffies_to_msecs(jiffies));
 	}
diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
index 4775b3a3dabe..7f0360d4e3a0 100644
--- a/mm/memory-tiers.c
+++ b/mm/memory-tiers.c
@@ -6,6 +6,7 @@
 #include <linux/memory.h>
 #include <linux/memory-tiers.h>
 #include <linux/notifier.h>
+#include <linux/sched/sysctl.h>
 
 #include "internal.h"
 
@@ -50,6 +51,22 @@ static const struct bus_type memory_tier_subsys = {
 	.dev_name = "memory_tier",
 };
 
+/**
+ * folio_has_cpupid - check if a folio has cpupid information
+ * @folio: folio to check
+ *
+ * folio's _last_cpupid field is repurposed by memory tiering. In memory
+ * tiering mode, cpupid of slow memory folio (not toptier memory) is used to
+ * record page access time.
+ *
+ * Return: the folio _last_cpupid is used as cpupid
+ */
+bool folio_has_cpupid(struct folio *folio)
+{
+	return !(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) ||
+	       node_is_toptier(folio_nid(folio));
+}
+
 #ifdef CONFIG_MIGRATION
 static int top_tier_adistance;
 /*
diff --git a/mm/memory.c b/mm/memory.c
index 802d0d8a40f9..105e1a0157dd 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5337,8 +5337,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 	 * For memory tiering mode, cpupid of slow memory page is used
 	 * to record page access time.  So use default value.
 	 */
-	if ((sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) &&
-	    !node_is_toptier(nid))
+	if (!folio_has_cpupid(folio))
 		last_cpupid = (-1 & LAST_CPUPID_MASK);
 	else
 		last_cpupid = folio_last_cpupid(folio);
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 222ab434da54..787c3c2bf1b6 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -161,8 +161,7 @@ static long change_pte_range(struct mmu_gather *tlb,
 				if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
 				    toptier)
 					continue;
-				if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
-				    !toptier)
+				if (!folio_has_cpupid(folio))
 					folio_xchg_access_time(folio,
 						jiffies_to_msecs(jiffies));
 			}
-- 
2.43.0

Re: [PATCH 2/2] memory tiering: introduce folio_has_cpupid() check

[Kefeng Wang]

On 2024/7/19 22:43, Zi Yan wrote:
> Instead of open coded check for if memory tiering mode is on and a folio
> is in the top tier memory, use a function to encapsulate the check.
> 
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
> ---
>   include/linux/memory-tiers.h |  8 ++++++++
>   kernel/sched/fair.c          |  3 +--
>   mm/huge_memory.c             |  6 ++----
>   mm/memory-tiers.c            | 17 +++++++++++++++++
>   mm/memory.c                  |  3 +--
>   mm/mprotect.c                |  3 +--
>   6 files changed, 30 insertions(+), 10 deletions(-)
> 
> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
> index 0dc0cf2863e2..10c127d461c4 100644
> --- a/include/linux/memory-tiers.h
> +++ b/include/linux/memory-tiers.h
> @@ -73,6 +73,10 @@ static inline bool node_is_toptier(int node)
>   }
>   #endif
>   
> +
> +bool folio_has_cpupid(struct folio *folio);
> +
> +
>   #else
>   
>   #define numa_demotion_enabled	false
> @@ -151,5 +155,9 @@ static inline struct memory_dev_type *mt_find_alloc_memory_type(int adist,
>   static inline void mt_put_memory_types(struct list_head *memory_types)
>   {
>   }
> +static inline bool folio_has_cpupid(struct folio *folio)
> +{
> +	return true;
> +}

Maybe better to move into mm.h since most folio_foo_cpupid()s are there?

Re: [PATCH 1/2] memory tiering: read last_cpupid correctly in do_huge_pmd_numa_page()

[Kefeng Wang]

On 2024/7/19 22:43, Zi Yan wrote:
> last_cpupid is only available when memory tiering is off or the folio
> is in toptier node. Complete the check to read last_cpupid when it is
> available.
> 
> Before the fix, the default last_cpupid will be used even if memory
> tiering mode is turned off at runtime instead of the actual value. This
> can prevent task_numa_fault() from getting right numa fault stats, but
> should not cause any crash. User might see performance changes after the
> fix.
> 
> Reported-by: David Hildenbrand <david@redhat.com>
> Closes: https://lore.kernel.org/linux-mm/9af34a6b-ca56-4a64-8aa6-ade65f109288@redhat.com/
> Fixes: 33024536bafd ("memory tiering: hot page selection with hint page fault latency")
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> Acked-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>

and we better to check numabalance mode in migrate_misplaced_folio()?

--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2630,7 +2630,8 @@ int migrate_misplaced_folio(struct folio *folio, 
struct vm_area_struct *vma,
                 putback_movable_pages(&migratepages);
         if (nr_succeeded) {
                 count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
-               if (!node_is_toptier(folio_nid(folio)) && 
node_is_toptier(node))
+               if ((sysctl_numa_balancing_mode & 
NUMA_BALANCING_MEMORY_TIERING)
+                   &&!node_is_toptier(folio_nid(folio)) && 
node_is_toptier(node))
                         mod_node_page_state(pgdat, PGPROMOTE_SUCCESS,
                                             nr_succeeded);
         }



> ---
>   mm/huge_memory.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index f4be468e06a4..825317aee88e 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1712,7 +1712,8 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
>   	 * For memory tiering mode, cpupid of slow memory page is used
>   	 * to record page access time.  So use default value.
>   	 */
> -	if (node_is_toptier(nid))
> +	if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) ||
> +	    node_is_toptier(nid))
>   		last_cpupid = folio_last_cpupid(folio);
>   	target_nid = numa_migrate_prep(folio, vmf, haddr, nid, &flags);
>   	if (target_nid == NUMA_NO_NODE)

Re: [PATCH 1/2] memory tiering: read last_cpupid correctly in do_huge_pmd_numa_page()

[Zi Yan]

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On 20 Jul 2024, at 4:11, Kefeng Wang wrote:

> On 2024/7/19 22:43, Zi Yan wrote:
>> last_cpupid is only available when memory tiering is off or the folio
>> is in toptier node. Complete the check to read last_cpupid when it is
>> available.
>>
>> Before the fix, the default last_cpupid will be used even if memory
>> tiering mode is turned off at runtime instead of the actual value. This
>> can prevent task_numa_fault() from getting right numa fault stats, but
>> should not cause any crash. User might see performance changes after the
>> fix.
>>
>> Reported-by: David Hildenbrand <david@redhat.com>
>> Closes: https://lore.kernel.org/linux-mm/9af34a6b-ca56-4a64-8aa6-ade65f109288@redhat.com/
>> Fixes: 33024536bafd ("memory tiering: hot page selection with hint page fault latency")
>> Signed-off-by: Zi Yan <ziy@nvidia.com>
>> Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
>> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> Acked-by: David Hildenbrand <david@redhat.com>
>
> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>
> and we better to check numabalance mode in migrate_misplaced_folio()?
>
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2630,7 +2630,8 @@ int migrate_misplaced_folio(struct folio *folio, struct vm_area_struct *vma,
>                 putback_movable_pages(&migratepages);
>         if (nr_succeeded) {
>                 count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
> -               if (!node_is_toptier(folio_nid(folio)) && node_is_toptier(node))
> +               if ((sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING)
> +                   &&!node_is_toptier(folio_nid(folio)) && node_is_toptier(node))
>                         mod_node_page_state(pgdat, PGPROMOTE_SUCCESS,
>                                             nr_succeeded);
>         }

Yes, will add this as a separate fix. Thanks.

--
Best Regards,
Yan, Zi

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Re: [PATCH 2/2] memory tiering: introduce folio_has_cpupid() check

[Zi Yan]

[-- Attachment #1: Type: text/plain, Size: 1550 bytes --]

On 20 Jul 2024, at 3:50, Kefeng Wang wrote:

> On 2024/7/19 22:43, Zi Yan wrote:
>> Instead of open coded check for if memory tiering mode is on and a folio
>> is in the top tier memory, use a function to encapsulate the check.
>>
>> Signed-off-by: Zi Yan <ziy@nvidia.com>
>> Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
>> ---
>>   include/linux/memory-tiers.h |  8 ++++++++
>>   kernel/sched/fair.c          |  3 +--
>>   mm/huge_memory.c             |  6 ++----
>>   mm/memory-tiers.c            | 17 +++++++++++++++++
>>   mm/memory.c                  |  3 +--
>>   mm/mprotect.c                |  3 +--
>>   6 files changed, 30 insertions(+), 10 deletions(-)
>>
>> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
>> index 0dc0cf2863e2..10c127d461c4 100644
>> --- a/include/linux/memory-tiers.h
>> +++ b/include/linux/memory-tiers.h
>> @@ -73,6 +73,10 @@ static inline bool node_is_toptier(int node)
>>   }
>>   #endif
>>  +
>> +bool folio_has_cpupid(struct folio *folio);
>> +
>> +
>>   #else
>>    #define numa_demotion_enabled	false
>> @@ -151,5 +155,9 @@ static inline struct memory_dev_type *mt_find_alloc_memory_type(int adist,
>>   static inline void mt_put_memory_types(struct list_head *memory_types)
>>   {
>>   }
>> +static inline bool folio_has_cpupid(struct folio *folio)
>> +{
>> +	return true;
>> +}
>
> Maybe better to move into mm.h since most folio_foo_cpupid()s are there?
Sounds good to me. Will do that in the next version.

--
Best Regards,
Yan, Zi

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