On Sun, Dec 06, 2020 at 06:14:48PM +0800, Muchun Song wrote:
> the global and per-node counters are stored in pages, however memcg
> and lruvec counters are stored in bytes. This scheme looks weird.
> So convert all vmstat slab counters to bytes.
There is a reason for this weird scheme:
percpu caches (see struct per_cpu_nodestat) are s8, so counting in bytes
will lead to overfills. Switching to s32 can lead to an increase in
the cache thrashing, especially on small machines.
>
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> ---
> include/linux/vmstat.h | 17 ++++++++++-------
> mm/vmstat.c | 21 ++++++++++-----------
> 2 files changed, 20 insertions(+), 18 deletions(-)
>
> diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> index 322dcbfcc933..fd1a3d5d4926 100644
> --- a/include/linux/vmstat.h
> +++ b/include/linux/vmstat.h
> @@ -197,18 +197,26 @@ static inline
> unsigned long global_node_page_state_pages(enum node_stat_item item)
> {
> long x = atomic_long_read(&vm_node_stat[item]);
> +
> #ifdef CONFIG_SMP
> if (x < 0)
> x = 0;
> #endif
> + if (vmstat_item_in_bytes(item))
> + x >>= PAGE_SHIFT;
> return x;
> }
>
> static inline unsigned long global_node_page_state(enum node_stat_item item)
> {
> - VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));
> + long x = atomic_long_read(&vm_node_stat[item]);
>
> - return global_node_page_state_pages(item);
> + VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));
> +#ifdef CONFIG_SMP
> + if (x < 0)
> + x = 0;
> +#endif
> + return x;
> }
>
> static inline unsigned long zone_page_state(struct zone *zone,
> @@ -312,11 +320,6 @@ static inline void __mod_zone_page_state(struct zone *zone,
> static inline void __mod_node_page_state(struct pglist_data *pgdat,
> enum node_stat_item item, int delta)
> {
> - if (vmstat_item_in_bytes(item)) {
> - VM_WARN_ON_ONCE(delta & (PAGE_SIZE - 1));
> - delta >>= PAGE_SHIFT;
> - }
> -
> node_page_state_add(delta, pgdat, item);
> }
>
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 8d77ee426e22..7fb0c7cb9516 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -345,11 +345,6 @@ void __mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
> long x;
> long t;
>
> - if (vmstat_item_in_bytes(item)) {
> - VM_WARN_ON_ONCE(delta & (PAGE_SIZE - 1));
> - delta >>= PAGE_SHIFT;
> - }
> -
> x = delta + __this_cpu_read(*p);
>
> t = __this_cpu_read(pcp->stat_threshold);
> @@ -554,11 +549,6 @@ static inline void mod_node_state(struct pglist_data *pgdat,
> s8 __percpu *p = pcp->vm_node_stat_diff + item;
> long o, n, t, z;
>
> - if (vmstat_item_in_bytes(item)) {
> - VM_WARN_ON_ONCE(delta & (PAGE_SIZE - 1));
> - delta >>= PAGE_SHIFT;
> - }
> -
> do {
> z = 0; /* overflow to node counters */
>
> @@ -1012,19 +1002,28 @@ unsigned long node_page_state_pages(struct pglist_data *pgdat,
> enum node_stat_item item)
> {
> long x = atomic_long_read(&pgdat->vm_stat[item]);
> +
> #ifdef CONFIG_SMP
> if (x < 0)
> x = 0;
> #endif
> + if (vmstat_item_in_bytes(item))
> + x >>= PAGE_SHIFT;
> return x;
> }
>
> unsigned long node_page_state(struct pglist_data *pgdat,
> enum node_stat_item item)
> {
> + long x = atomic_long_read(&pgdat->vm_stat[item]);
> +
> VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));
>
> - return node_page_state_pages(pgdat, item);
> +#ifdef CONFIG_SMP
> + if (x < 0)
> + x = 0;
> +#endif
> + return x;
> }
> #endif
>
> --
> 2.11.0
>
