Yang Shi <[email protected]> writes:

> On Wed, Oct 13, 2021 at 5:50 PM Huang, Ying <[email protected]> wrote:
>>
>> Yang Shi <[email protected]> writes:
>>
>> > On Fri, Oct 8, 2021 at 1:40 AM Huang Ying <[email protected]> wrote:
>> >>
>> >> In a system with multiple memory types, e.g. DRAM and PMEM, the CPU
>> >> and DRAM in one socket will be put in one NUMA node as before, while
>> >> the PMEM will be put in another NUMA node as described in the
>> >> description of the commit c221c0b0308f ("device-dax: "Hotplug"
>> >> persistent memory for use like normal RAM"). So, the NUMA balancing
>> >> mechanism will identify all PMEM accesses as remote access and try to
>> >> promote the PMEM pages to DRAM.
>> >>
>> >> To distinguish the number of the inter-type promoted pages from that
>> >> of the inter-socket migrated pages. A new vmstat count is added. The
>> >> counter is per-node (count in the target node). So this can be used
>> >> to identify promotion imbalance among the NUMA nodes.
>> >>
>> >> Signed-off-by: "Huang, Ying" <[email protected]>
>> >> Cc: Andrew Morton <[email protected]>
>> >> Cc: Michal Hocko <[email protected]>
>> >> Cc: Rik van Riel <[email protected]>
>> >> Cc: Mel Gorman <[email protected]>
>> >> Cc: Peter Zijlstra <[email protected]>
>> >> Cc: Dave Hansen <[email protected]>
>> >> Cc: Yang Shi <[email protected]>
>> >> Cc: Zi Yan <[email protected]>
>> >> Cc: Wei Xu <[email protected]>
>> >> Cc: osalvador <[email protected]>
>> >> Cc: Shakeel Butt <[email protected]>
>> >> Cc: [email protected]
>> >> Cc: [email protected]
>> >> ---
>> >> include/linux/mmzone.h | 3 +++
>> >> include/linux/node.h | 5 +++++
>> >> include/linux/vmstat.h | 2 ++
>> >> mm/migrate.c | 10 ++++++++--
>> >> mm/vmstat.c | 3 +++
>> >> 5 files changed, 21 insertions(+), 2 deletions(-)
>> >>
>> >> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> >> index 6a1d79d84675..37ccd6158765 100644
>> >> --- a/include/linux/mmzone.h
>> >> +++ b/include/linux/mmzone.h
>> >> @@ -209,6 +209,9 @@ enum node_stat_item {
>> >> NR_PAGETABLE, /* used for pagetables */
>> >> #ifdef CONFIG_SWAP
>> >> NR_SWAPCACHE,
>> >> +#endif
>> >> +#ifdef CONFIG_NUMA_BALANCING
>> >> + PGPROMOTE_SUCCESS, /* promote successfully */
>> >> #endif
>> >> NR_VM_NODE_STAT_ITEMS
>> >> };
>> >> diff --git a/include/linux/node.h b/include/linux/node.h
>> >> index 8e5a29897936..26e96fcc66af 100644
>> >> --- a/include/linux/node.h
>> >> +++ b/include/linux/node.h
>> >> @@ -181,4 +181,9 @@ 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/include/linux/vmstat.h b/include/linux/vmstat.h
>> >> index d6a6cf53b127..75c53b7d1539 100644
>> >> --- a/include/linux/vmstat.h
>> >> +++ b/include/linux/vmstat.h
>> >> @@ -112,9 +112,11 @@ static inline void vm_events_fold_cpu(int cpu)
>> >> #ifdef CONFIG_NUMA_BALANCING
>> >> #define count_vm_numa_event(x) count_vm_event(x)
>> >> #define count_vm_numa_events(x, y) count_vm_events(x, y)
>> >> +#define mod_node_balancing_page_state(n, i, v) mod_node_page_state(n, i, v)
>> >
>> > I don't quite get why we need this new API. Doesn't __count_vm_events() work?
>>
>> PGPROMOTE_SUCCESS is a per-node counter. That is, its type is enum
>> node_stat_item instead of enum vm_event_item. So we need to use
>> mod_node_page_state() instead of count_vm_events(). The new API is to
>> avoid #ifdef CONFIG_NUMA_BALANCING/#endif in caller.
>
> Aha, I see, sorry for overlooking this. But I think you could just
> call mod_node_page_state() since migrate_misplaced_page() has been
> protected by #ifdef CONFIG_NUMA_BALANCING. The !CONFIG_NUMA_BALANCING
> version just returns -EFAULT. Other than this, another nit below.
>

Yes. You are right. I will use mod_node_page_state() directly!

>>
>> >> #else
>> >> #define count_vm_numa_event(x) do {} while (0)
>> >> #define count_vm_numa_events(x, y) do { (void)(y); } while (0)
>> >> +#define mod_node_balancing_page_state(n, i, v) do {} while (0)
>> >> #endif /* CONFIG_NUMA_BALANCING */
>> >>
>> >> #ifdef CONFIG_DEBUG_TLBFLUSH
>> >> diff --git a/mm/migrate.c b/mm/migrate.c
>> >> index a6a7743ee98f..c3affc587902 100644
>> >> --- a/mm/migrate.c
>> >> +++ b/mm/migrate.c
>> >> @@ -2148,6 +2148,7 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
>> >> pg_data_t *pgdat = NODE_DATA(node);
>> >> int isolated;
>> >> int nr_remaining;
>> >> + int nr_succeeded;
>> >> LIST_HEAD(migratepages);
>> >> new_page_t *new;
>> >> bool compound;
>> >> @@ -2186,7 +2187,8 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
>> >>
>> >> list_add(&page->lru, &migratepages);
>> >> nr_remaining = migrate_pages(&migratepages, *new, NULL, node,
>> >> - MIGRATE_ASYNC, MR_NUMA_MISPLACED, NULL);
>> >> + MIGRATE_ASYNC, MR_NUMA_MISPLACED,
>> >> + &nr_succeeded);
>> >> if (nr_remaining) {
>> >> if (!list_empty(&migratepages)) {
>> >> list_del(&page->lru);
>> >> @@ -2195,8 +2197,12 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
>> >> putback_lru_page(page);
>> >> }
>> >> isolated = 0;
>> >> - } else
>> >> + } else {
>> >> count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_pages);
>> >> + if (!node_is_toptier(page_to_nid(page)) && node_is_toptier(node))
>> >> + mod_node_balancing_page_state(
>> >> + NODE_DATA(node), PGPROMOTE_SUCCESS, nr_succeeded);
>> >> + }
>
> It looks the original code is already problematic. It just updates the
> counter when *all* pages are migrated successfully. But since we
> already has "nr_succeeded", so I think we could do:
>
> if (nr_remaining) {
> do_something();
> }
>
> count_vm_numa_events(NUMA_PAGE_MIGRATE, nr_succeeded);
> if (!node_is_toptier(page_to_nid(page)) && node_is_toptier(node))
> mod_node_page_state(NODE_DATA(node), PGPROMOTE_SUCCESS, nr_succeeded);

Looks good to me. Will update this in the next version.

Best Regards,
Huang, Ying

>> >> BUG_ON(!list_empty(&migratepages));
>> >> return isolated;
>> >>
>> >> diff --git a/mm/vmstat.c b/mm/vmstat.c
>> >> index 8ce2620344b2..fff0ec94d795 100644
>> >> --- a/mm/vmstat.c
>> >> +++ b/mm/vmstat.c
>> >> @@ -1236,6 +1236,9 @@ const char * const vmstat_text[] = {
>> >> #ifdef CONFIG_SWAP
>> >> "nr_swapcached",
>> >> #endif
>> >> +#ifdef CONFIG_NUMA_BALANCING
>> >> + "pgpromote_success",
>> >> +#endif
>> >>
>> >> /* enum writeback_stat_item counters */
>> >> "nr_dirty_threshold",
>> >> --
>> >> 2.30.2
>> >>