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SubjectRe: [patch -mm] mm, memcg: evaluate root and leaf memcgs fairly on oom
On Wed, Mar 14, 2018 at 01:41:03PM -0700, David Rientjes wrote:
> On Wed, 14 Mar 2018, Roman Gushchin wrote:
>
> > > @@ -2618,92 +2620,65 @@ static long memcg_oom_badness(struct mem_cgroup *memcg,
> > > if (nodemask && !node_isset(nid, *nodemask))
> > > continue;
> > >
> > > - points += mem_cgroup_node_nr_lru_pages(memcg, nid,
> > > - LRU_ALL_ANON | BIT(LRU_UNEVICTABLE));
> > > -
> > > pgdat = NODE_DATA(nid);
> > > - points += lruvec_page_state(mem_cgroup_lruvec(pgdat, memcg),
> > > - NR_SLAB_UNRECLAIMABLE);
> > > + if (is_root_memcg) {
> > > + points += node_page_state(pgdat, NR_ACTIVE_ANON) +
> > > + node_page_state(pgdat, NR_INACTIVE_ANON);
> > > + points += node_page_state(pgdat, NR_SLAB_UNRECLAIMABLE);
> > > + } else {
> > > + points += mem_cgroup_node_nr_lru_pages(memcg, nid,
> > > + LRU_ALL_ANON);
> > > + points += lruvec_page_state(mem_cgroup_lruvec(pgdat, memcg),
> > > + NR_SLAB_UNRECLAIMABLE);
> > > + }
> > > }
> > >
> > > - points += memcg_page_state(memcg, MEMCG_KERNEL_STACK_KB) /
> > > - (PAGE_SIZE / 1024);
> > > - points += memcg_page_state(memcg, MEMCG_SOCK);
> > > - points += memcg_page_state(memcg, MEMCG_SWAP);
> > > -
> > > + if (is_root_memcg) {
> > > + points += global_zone_page_state(NR_KERNEL_STACK_KB) /
> > > + (PAGE_SIZE / 1024);
> > > + points += atomic_long_read(&total_sock_pages);
> > ^^^^^^^^^^^^^^^^
> > BTW, where do we change this counter?
> >
>
> Seems like it was dropped from the patch somehow. It is intended to do
> atomic_long_add(nr_pages) in mem_cgroup_charge_skmem() and
> atomic_long_add(-nr_pages) mem_cgroup_uncharge_skmem().
>
> > I also doubt that global atomic variable can work here,
> > we probably need something better scaling.
> >
>
> Why do you think an atomic_long_add() is too expensive when we're already
> disabling irqs and dong try_charge()?

Hard to say without having full code :)
try_charge() is batched, if you'll batch it too, it will probably work.

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