On Tue, Dec 8, 2020 at 3:46 AM Roman Gushchin <g...@fb.com> wrote:
>
> 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.
Thanks Roman. I see now.
>
> >
> > Signed-off-by: Muchun Song <songmuc...@bytedance.com>
> > ---
> > 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
> >
--
Yours,
Muchun
