Messages in this thread | | | Date | Wed, 26 Jul 2023 11:13:15 -0400 | From | Johannes Weiner <> | Subject | Re: [PATCH v2] mm: memcg: use rstat for non-hierarchical stats |
| |
On Tue, Jul 25, 2023 at 05:36:45PM -0700, Yosry Ahmed wrote: > On Tue, Jul 25, 2023 at 5:29 PM Yosry Ahmed <yosryahmed@google.com> wrote: > > - Fix a subtle bug where updating a local counter would be missed if it > > was cancelled out by a pending update from child memcgs. > > > Johannes, I fixed a subtle bug here and I kept your Ack, I wasn't sure > what the Ack retention policy should be here. A quick look at the fix > would be great.
Ah, I found it:
> > @@ -5542,19 +5539,23 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu) > > memcg->vmstats->state_pending[i] = 0; > > > > /* Add CPU changes on this level since the last flush */ > > + delta_cpu = 0; > > v = READ_ONCE(statc->state[i]); > > if (v != statc->state_prev[i]) { > > - delta += v - statc->state_prev[i]; > > + delta_cpu = v - statc->state_prev[i]; > > + delta += delta_cpu; > > statc->state_prev[i] = v; > > } > > > > - if (!delta) > > - continue; > > - > > /* Aggregate counts on this level and propagate upwards */ > > - memcg->vmstats->state[i] += delta; > > - if (parent) > > - parent->vmstats->state_pending[i] += delta; > > + if (delta_cpu) > > + memcg->vmstats->state_local[i] += delta_cpu;
When delta nulls out, but delta_cpu is non-zero... subtle.
This fixed version looks good, please keep my ack :)
| |