Hi, > -----Original Message----- > From: Michal Hocko [mailto:mstsxfx@xxxxxxxxx] On Behalf Of Michal Hocko > Sent: Monday, February 02, 2015 5:45 PM > To: PINTU KUMAR > Cc: cgroups@xxxxxxxxxxxxxxx; bsingharora@xxxxxxxxx; > kamezawa.hiroyu@xxxxxxxxxxxxxx; hannes@xxxxxxxxxxx; xemul@xxxxxxxxxx; > cpgs@xxxxxxxxxxx > Subject: Re: CGROUPS: HowTo: perform force_empty > > On Mon 02-02-15 15:23:22, PINTU KUMAR wrote: > > Hi, > > > > I have a question about memory cgroups under Linux kernel 3.10. > > Under: /sys/fs/cgroup/memory/: > > > > I found, memory.force_empty. > > But, when I try to do the following it says invalid argument: > > # echo 0 > memory.force_empty > > sh: echo: write error: Invalid argument > > > > It even fails with "echo 1" > > It is not clear on which cgroup you are trying to invoke force_empty. > The knob is disabled for the root memcg so I suppose this is why you see the failure. > Ok, please let me know how to use it for specific group, and where to check the group info. Also, why we should not run it for: root_mem_cgroup > > I am using this command from the shell using the root login. > > Can you tell me how to execute the force_empty command. > > You can echo anything to the knob to trigger the reclaim. > > > Or, how to release all the memory under all cgroups and release it to > > the system? > > Why would you use memcg API to release memory from the system as whole? > What are you trying to achieve? > Actually, the problem is that, the system is running with low memory, after few application launch. When, I see the cgroup: memory.stat, lots are memory is available in cgroups. I also observed that system performs force_reclaim in background, to reclaim some memory from the background cgroup. But, at some scenario, I wanted to clean-up entire cgroup and start from fresh, without killing the application, or without rebooting the system. This is only for some experiment purpose. > > Under, mm/memcontrol.c , if I use the function: > > mem_cgroup_force_empty(struct mem_cgroup *memcg), will it help to release > all memory? > > But, then, how to initialize the memcg data structure? > > Can you provide some example to use this API, from some other kernel > > sub-system. > > mem_cgroup_force_empty is an internal memory controller functionality which is > not supposed to be used from other kernel subsystems. Why would you want to > force reclaim on memcg level from the kernel in the first place? I observe that force reclaim is already happening, during low memory condition. Similarly, I want to use force_empty option. But, I worry about, how to initialize the : struct mem_cgroup *memcg What field, and what value I should set in this structure, to pass to force_empty. This is only for some experiment purpose. Otherwise, please let me know, how to use the: try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, ....), which is found in mm/vmscan.c In any case, I need to know how to initialize the mem_cgroup structure. Once the experiment results are successful, I will share the details back. Thank you for your reply. > -- > Michal Hocko > SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
