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Message-ID: <CAHbLzkpkP1McCqzLuJ8uFbZfB3DNj7EBis6Q+0oS-mg1xYUfHQ@mail.gmail.com>
Date: Thu, 14 Oct 2021 15:52:10 -0700
From: Yang Shi <shy828301@...il.com>
To: "Huang, Ying" <ying.huang@...el.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Michal Hocko <mhocko@...e.com>,
Rik van Riel <riel@...riel.com>,
Mel Gorman <mgorman@...e.de>,
Peter Zijlstra <peterz@...radead.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Zi Yan <ziy@...dia.com>, Wei Xu <weixugc@...gle.com>,
osalvador <osalvador@...e.de>,
Shakeel Butt <shakeelb@...gle.com>,
Linux MM <linux-mm@...ck.org>
Subject: Re: [PATCH -V9 1/6] NUMA Balancing: add page promotion counter
On Wed, Oct 13, 2021 at 5:50 PM Huang, Ying <ying.huang@...el.com> wrote:
>
> Yang Shi <shy828301@...il.com> writes:
>
> > On Fri, Oct 8, 2021 at 1:40 AM Huang Ying <ying.huang@...el.com> 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" <ying.huang@...el.com>
> >> Cc: Andrew Morton <akpm@...ux-foundation.org>
> >> Cc: Michal Hocko <mhocko@...e.com>
> >> Cc: Rik van Riel <riel@...riel.com>
> >> Cc: Mel Gorman <mgorman@...e.de>
> >> Cc: Peter Zijlstra <peterz@...radead.org>
> >> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> >> Cc: Yang Shi <shy828301@...il.com>
> >> Cc: Zi Yan <ziy@...dia.com>
> >> Cc: Wei Xu <weixugc@...gle.com>
> >> Cc: osalvador <osalvador@...e.de>
> >> Cc: Shakeel Butt <shakeelb@...gle.com>
> >> Cc: linux-kernel@...r.kernel.org
> >> Cc: linux-mm@...ck.org
> >> ---
> >> 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.
>
> Best Regards,
> Huang, Ying
>
> >> #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);
> >> 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
> >>
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