Re: [PATCH v11 8/8] mm/demotion: Update node_is_toptier to work with memory tiers

Aneesh Kumar K V
2022-07-29T06:48:21Z

On 7/29/22 12:11 PM, Aneesh Kumar K V wrote:
> On 7/29/22 12:09 PM, Huang, Ying wrote:
>> "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> writes:
>>
>>> With memory tiers support we can have memory only NUMA nodes
>>> in the top tier from which we want to avoid promotion tracking NUMA
>>> faults. Update node_is_toptier to work with memory tiers.
>>> All NUMA nodes are by default top tier nodes. With lower memory
>>> tiers added we consider all memory tiers above a memory tier having
>>> CPU NUMA nodes as a top memory tier
>>>
>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
>>> ---
>>> include/linux/memory-tiers.h | 11 ++++++++++
>>> include/linux/node.h | 5 -----
>>> mm/huge_memory.c | 1 +
>>> mm/memory-tiers.c | 42 ++++++++++++++++++++++++++++++++++++
>>> mm/migrate.c | 1 +
>>> mm/mprotect.c | 1 +
>>> 6 files changed, 56 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/include/linux/memory-tiers.h b/include/linux/memory-tiers.h
>>> index f8dbeda617a7..bc9fb9d39b2c 100644
>>> --- a/include/linux/memory-tiers.h
>>> +++ b/include/linux/memory-tiers.h
>>> @@ -35,6 +35,7 @@ struct memory_dev_type *init_node_memory_type(int node, struct memory_dev_type *
>>> #ifdef CONFIG_MIGRATION
>>> int next_demotion_node(int node);
>>> void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets);
>>> +bool node_is_toptier(int node);
>>> #else
>>> static inline int next_demotion_node(int node)
>>> {
>>> @@ -45,6 +46,11 @@ static inline void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *target
>>> {
>>> *targets = NODE_MASK_NONE;
>>> }
>>> +
>>> +static inline bool node_is_toptier(int node)
>>> +{
>>> + return true;
>>> +}
>>> #endif
>>>
>>> #else
>>> @@ -64,5 +70,10 @@ static inline void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *target
>>> {
>>> *targets = NODE_MASK_NONE;
>>> }
>>> +
>>> +static inline bool node_is_toptier(int node)
>>> +{
>>> + return true;
>>> +}
>>> #endif /* CONFIG_NUMA */
>>> #endif /* _LINUX_MEMORY_TIERS_H */
>>> diff --git a/include/linux/node.h b/include/linux/node.h
>>> index 40d641a8bfb0..9ec680dd607f 100644
>>> --- a/include/linux/node.h
>>> +++ b/include/linux/node.h
>>> @@ -185,9 +185,4 @@ static inline void register_hugetlbfs_with_node(node_registration_func_t reg,
>>>
>>> #define to_node(device) container_of(device, struct node, dev)
>>>
>>> -static inline bool node_is_toptier(int node)
>>> -{
>>> - return node_state(node, N_CPU);
>>> -}
>>> -
>>> #endif /* _LINUX_NODE_H_ */
>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>>> index 834f288b3769..8405662646e9 100644
>>> --- a/mm/huge_memory.c
>>> +++ b/mm/huge_memory.c
>>> @@ -35,6 +35,7 @@
>>> #include <linux/numa.h>
>>> #include <linux/page_owner.h>
>>> #include <linux/sched/sysctl.h>
>>> +#include <linux/memory-tiers.h>
>>>
>>> #include <asm/tlb.h>
>>> #include <asm/pgalloc.h>
>>> diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
>>> index 84e2be31a853..36d87dc422ab 100644
>>> --- a/mm/memory-tiers.c
>>> +++ b/mm/memory-tiers.c
>>> @@ -30,6 +30,7 @@ static DEFINE_MUTEX(memory_tier_lock);
>>> static LIST_HEAD(memory_tiers);
>>> struct memory_dev_type *node_memory_types[MAX_NUMNODES];
>>> #ifdef CONFIG_MIGRATION
>>> +static int top_tier_adistance;
>>> /*
>>> * node_demotion[] examples:
>>> *
>>> @@ -159,6 +160,31 @@ static struct memory_tier *__node_get_memory_tier(int node)
>>> }
>>>
>>> #ifdef CONFIG_MIGRATION
>>> +bool node_is_toptier(int node)
>>> +{
>>> + bool toptier;
>>> + pg_data_t *pgdat;
>>> + struct memory_tier *memtier;
>>> +
>>> + pgdat = NODE_DATA(node);
>>> + if (!pgdat)
>>> + return false;
>>> +
>>> + rcu_read_lock();
>>> + memtier = rcu_dereference(pgdat->memtier);
>>> + if (!memtier) {
>>> + toptier = true;
>>> + goto out;
>>> + }
>>> + if (memtier->adistance_start >= top_tier_adistance)
>>> + toptier = true;
>>> + else
>>> + toptier = false;
>>> +out:
>>> + rcu_read_unlock();
>>> + return toptier;
>>> +}
>>> +
>>> void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets)
>>> {
>>> struct memory_tier *memtier;
>>> @@ -315,6 +341,22 @@ static void establish_demotion_targets(void)
>>> }
>>> } while (1);
>>> }
>>> + /*
>>> + * Promotion is allowed from a memory tier to higher
>>> + * memory tier only if the memory tier doesn't include
>>> + * compute. We want to skip promotion from a memory tier,
>>> + * if any node that is part of the memory tier have CPUs.
>>> + * Once we detect such a memory tier, we consider that tier
>>> + * as top tiper from which promotion on is not allowed.
>>> + */
>>> + list_for_each_entry(memtier, &memory_tiers, list) {
>>> + tier_nodes = get_memtier_nodemask(memtier);
>>> + nodes_and(tier_nodes, node_states[N_CPU], tier_nodes);
>>> + if (!nodes_empty(tier_nodes)) {
>>> + top_tier_adistance = memtier->adistance_start;
>>
>> IMHO, this should be,
>>
>> top_tier_adistance = memtier->adistance_start + MEMTIER_CHUNK_SIZE;
>>
>
> Good catch. Will update. BTW i did send v12 version of the patchset already to the list.
>
>

Checking this again, we consider a node top tier if the node's memtier abstract distance
satisfy the below.

if (memtier->adistance_start <= top_tier_adistance)
toptier = true;

With that we should be good with the current code. But I agree with you that top_tier_distance
should cover the full range of the top memory tier.

-aneesh