Messages in this thread | | | Date | Thu, 5 Nov 2020 10:50:28 -0500 | From | Johannes Weiner <> | Subject | Re: [PATCH] mm: memcontrol: fix missing wakeup polling thread |
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On Wed, Nov 04, 2020 at 08:55:58PM +0800, Muchun Song wrote: > When wen poll the memory.swap.events, we can miss being waked up when the > swap event occurs. Because we didn't notify. > > Fixes: f3a53a3a1e5b ("mm, memcontrol: implement memory.swap.events") > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Good catch!
> --- > include/linux/memcontrol.h | 18 ++++++++++++++++-- > 1 file changed, 16 insertions(+), 2 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index 0f4dd7829fb2..2456cb737329 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -1071,15 +1071,29 @@ static inline void count_memcg_event_mm(struct mm_struct *mm, > rcu_read_unlock(); > } > > +static inline bool is_swap_memory_event(enum memcg_memory_event event) > +{ > + return event == MEMCG_SWAP_HIGH || event == MEMCG_SWAP_MAX || > + event == MEMCG_SWAP_FAIL; > +}
Please inline this, it's not really worth the indirection.
> static inline void memcg_memory_event(struct mem_cgroup *memcg, > enum memcg_memory_event event) > { > + bool swap_event = is_swap_memory_event(event); > + struct cgroup_file *cfile; > + > atomic_long_inc(&memcg->memory_events_local[event]); > - cgroup_file_notify(&memcg->events_local_file); > + if (swap_event) { > + cfile = &memcg->swap_events_file; > + } else { > + cfile = &memcg->events_file; > + cgroup_file_notify(&memcg->events_local_file); > + } > > do { > atomic_long_inc(&memcg->memory_events[event]); > - cgroup_file_notify(&memcg->events_file); > + cgroup_file_notify(cfile);
This loop is a walk up the hierarchy and memcg keeps changing, so you cannot cache cfile up front.
if (swap_event) cgroup_file_notify(&memcg->swap_events_file); else cgroup_file_notify(&memcg->events_file);
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