| Message ID | 20200915132741.84869-1-zangchunxin@bytedance.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4] mm/vmscan: add a fatal signals check in drop_slab_node | expand |
On Tue 15-09-20 21:27:41, zangchunxin@bytedance.com wrote: > From: Chunxin Zang <zangchunxin@bytedance.com> > > On our server, there are about 10k memcg in one machine. They use memory > very frequently. We have observed that drop_caches can take a > considerable amount of time, and can't stop it. > > There are two reasons: > 1. There is somebody constantly generating more objects to reclaim > on drop_caches, result the 'freed' always bigger than 10. > 2. The process has no chance to process signals. > > We can get the following info through 'ps': > > root:~# ps -aux | grep drop > root 357956 ... R Aug25 21119854:55 echo 3 > /proc/sys/vm/drop_caches > root 1771385 ... R Aug16 21146421:17 echo 3 > /proc/sys/vm/drop_caches > > Add a bail out on the fatal signals in the main loop so that the > operation can be terminated by userspace. > > Signed-off-by: Chunxin Zang <zangchunxin@bytedance.com> > Signed-off-by: Muchun Song <songmuchun@bytedance.com> Acked-by: Michal Hocko <mhocko@suse.com> > --- > > changelogs in v4: > changelogs in v3: > 1) Fix some descriptive problems pointed out by Michal Hocko. > v2 named: mm/vmscan: fix infinite loop in drop_slab_node > > changelogs in v2: > 1) via check fatal signal break loop. > > mm/vmscan.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index b6d84326bdf2..6b2b5d420510 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -704,6 +704,9 @@ void drop_slab_node(int nid) > do { > struct mem_cgroup *memcg = NULL; > > + if (signal_pending(current)) > + return; > + > freed = 0; > memcg = mem_cgroup_iter(NULL, NULL, NULL); > do { > -- > 2.11.0 >
zangchunxin@bytedance.com writes: >+ if (signal_pending(current)) >+ return; This doesn't match your patch title, please update it. :-) After that, you can add: Acked-by: Chris Down <chris@chrisdown.name>
On Tue 15-09-20 15:47:37, Chris Down wrote: > zangchunxin@bytedance.com writes: > > + if (signal_pending(current)) > > + return; > > This doesn't match your patch title, please update it. :-) I have to admit I have completely missed this and I think that this should better be fatal_signal_pending because that would make sure that the userspace will not see an incomplete operation. This is a general practice for other bail outs as well. > After that, you can add: > > Acked-by: Chris Down <chris@chrisdown.name>
Michal Hocko writes: >On Tue 15-09-20 15:47:37, Chris Down wrote: >> zangchunxin@bytedance.com writes: >> > + if (signal_pending(current)) >> > + return; >> >> This doesn't match your patch title, please update it. :-) > >I have to admit I have completely missed this and I think that this >should better be fatal_signal_pending because that would make sure that >the userspace will not see an incomplete operation. This is a general >practice for other bail outs as well. Oh sorry, to be clear, I meant the patch should match the title, not the other way around.
On Wed, Sep 16, 2020 at 12:26 AM Chris Down <chris@chrisdown.name> wrote: > > Michal Hocko writes: > >On Tue 15-09-20 15:47:37, Chris Down wrote: > >> zangchunxin@bytedance.com writes: > >> > + if (signal_pending(current)) > >> > + return; > >> > >> This doesn't match your patch title, please update it. :-) > > > >I have to admit I have completely missed this and I think that this > >should better be fatal_signal_pending because that would make sure that > >the userspace will not see an incomplete operation. This is a general > >practice for other bail outs as well. > > Oh sorry, to be clear, I meant the patch should match the title, not the other > way around. My apologies about that. In my first version of patch, it's 'fatal_signal_pending'. But in this version, I used the wrong branch. I will update it now. Best wishes Chunxin
diff --git a/mm/vmscan.c b/mm/vmscan.c index b6d84326bdf2..6b2b5d420510 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -704,6 +704,9 @@ void drop_slab_node(int nid) do { struct mem_cgroup *memcg = NULL; + if (signal_pending(current)) + return; + freed = 0; memcg = mem_cgroup_iter(NULL, NULL, NULL); do {