> -----邮件原件----- > 发件人: Michal Hocko [mailto:mhocko@xxxxxxxxxx] > 发送时间: 2018年3月19日 18:38 > 收件人: Li,Rongqing <lirongqing@xxxxxxxxx> > 抄送: linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; > cgroups@xxxxxxxxxxxxxxx; hannes@xxxxxxxxxxx; Andrey Ryabinin > <aryabinin@xxxxxxxxxxxxx> > 主题: Re: 答复: [PATCH] mm/memcontrol.c: speed up to force empty a > memory cgroup > > On Mon 19-03-18 10:00:41, Li,Rongqing wrote: > > > > > > > -----邮件原件----- > > > 发件人: Michal Hocko [mailto:mhocko@xxxxxxxxxx] > > > 发送时间: 2018年3月19日 16:54 > > > 收件人: Li,Rongqing <lirongqing@xxxxxxxxx> > > > 抄送: linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; > > > cgroups@xxxxxxxxxxxxxxx; hannes@xxxxxxxxxxx; Andrey Ryabinin > > > <aryabinin@xxxxxxxxxxxxx> > > > 主题: Re: [PATCH] mm/memcontrol.c: speed up to force empty a > memory > > > cgroup > > > > > > On Mon 19-03-18 16:29:30, Li RongQing wrote: > > > > mem_cgroup_force_empty() tries to free only 32 > (SWAP_CLUSTER_MAX) > > > > pages on each iteration, if a memory cgroup has lots of page > > > > cache, it will take many iterations to empty all page cache, so > > > > increase the reclaimed number per iteration to speed it up. same > > > > as in > > > > mem_cgroup_resize_limit() > > > > > > > > a simple test show: > > > > > > > > $dd if=aaa of=bbb bs=1k count=3886080 > > > > $rm -f bbb > > > > $time echo > 100000000 >/cgroup/memory/test/memory.limit_in_bytes > > > > > > > > Before: 0m0.252s ===> after: 0m0.178s > > > > > > Andrey was proposing something similar [1]. My main objection was > > > that his approach might lead to over-reclaim. Your approach is more > > > conservative because it just increases the batch size. The size is > > > still rather arbitrary. Same as SWAP_CLUSTER_MAX but that one is a > > > commonly used unit of reclaim in the MM code. > > > > > > I would be really curious about more detailed explanation why having > > > a larger batch yields to a better performance because we are doingg > > > SWAP_CLUSTER_MAX batches at the lower reclaim level anyway. > > > > > > > Although SWAP_CLUSTER_MAX is used at the lower level, but the call > > stack of try_to_free_mem_cgroup_pages is too long, increase the > > nr_to_reclaim can reduce times of calling > > function[do_try_to_free_pages, shrink_zones, hrink_node ] > > > > mem_cgroup_resize_limit > > --->try_to_free_mem_cgroup_pages: .nr_to_reclaim = max(1024, > > --->SWAP_CLUSTER_MAX), > > ---> do_try_to_free_pages > > ---> shrink_zones > > --->shrink_node > > ---> shrink_node_memcg > > ---> shrink_list <-------loop will happen in this place > [times=1024/32] > > ---> shrink_page_list > > Can you actually measure this to be the culprit. Because we should rethink > our call path if it is too complicated/deep to perform well. > Adding arbitrary batch sizes doesn't sound like a good way to go to me. Ok, I will try -RongQing > -- > Michal Hocko > SUSE Labs
