> -----邮件原件----- > 发件人: Michal Hocko [mailto:mhocko@xxxxxxxxxx] > 发送时间: 2018年4月3日 16:05 > 收件人: Li,Rongqing <lirongqing@xxxxxxxxx> > 抄送: hannes@xxxxxxxxxxx; vdavydov.dev@xxxxxxxxx; > cgroups@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx > 主题: Re: [PATCH] mm: avoid the unnecessary waiting when force empty a > cgroup > > On Tue 03-04-18 15:12:09, Li RongQing wrote: > > The number of writeback and dirty page can be read out from memcg, the > > unnecessary waiting can be avoided by these counts > > This changelog doesn't explain the problem and how the patch fixes it. If a process in a memory cgroup takes some RSS, when force empty this memory cgroup, congestion_wait will be called unconditionally, there is 0.5 seconds delay If use this patch, nearly no delay. > Why do wee another throttling when we do already throttle in the reclaim > path? Do you mean we should remove congestion_wait(BLK_RW_ASYNC, HZ/10) from mem_cgroup_force_empty, since try_to_free_mem_cgroup_pages [shrink_inactive_list] has called congestion_wait -RongQing > > > Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx> > > --- > > mm/memcontrol.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c index > > 9ec024b862ac..5258651bd4ec 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -2613,9 +2613,13 @@ static int mem_cgroup_force_empty(struct > mem_cgroup *memcg) > > progress = try_to_free_mem_cgroup_pages(memcg, 1, > > GFP_KERNEL, true); > > if (!progress) { > > + unsigned long num; > > + > > + num = memcg_page_state(memcg, NR_WRITEBACK) + > > + memcg_page_state(memcg, NR_FILE_DIRTY); > > nr_retries--; > > - /* maybe some writeback is necessary */ > > - congestion_wait(BLK_RW_ASYNC, HZ/10); > > + if (num) > > + congestion_wait(BLK_RW_ASYNC, HZ/10); > > } > > > > } > > -- > > 2.11.0 > > -- > Michal Hocko > SUSE Labs
