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

Huang, Ying
2022-08-01T01:04:32Z

Aneesh Kumar K V <aneesh.kumar@linux.ibm.com> writes:

> 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;

I admit that this works correctly. And I think that the following code
is even more correct conceptually. If so, why not help the code reader
to understand it more easily?

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

Best Regards,
Huang, Ying

> 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