[lxc-devel] the solution of top and free in the lxc

[Serge Hallyn]

Quoting 魏子然 (duck_uuu at 163.com):
> Hello, we encounter a problem in the use of lxc, that the command of  free and top does 
> not show container\'s cpu and memory but the host server\'s;we know that it is a problem 
> of proc directory which is mounted outside the container with remount option.we also 

Being mounted outside the container isn't the problem.  The problem,
depending on who you ask, is that the tools want /proc to be something
it isn't.  The ideal, according to kernel community, would be for
someone to write a new library which can integrate the /proc and
cgroup information to give the desired information to userspace
tools like top and free - not to keep trying to paper over /proc.

That said, after many years noone has sat down and volunteered their
time to actually write such a library and propose patches to the
rest of upstream (top etc) to use those - so papering over /proc
still is appealing :)

> know that we can solve this problem with fuse.
> 
> now we put forward another solution which is also based on fuse,but with more 
> difference,our solution is modify lxc-start.c:
> before do_clone() we use fuse to generate a userspaces proc filesystem,call mount() to 
> mount /lxc/as6.3/proc directory;
> after perform mount_rootfs_dir ($rootfs, $target) ,then call mount() to mount 
> /lxc/as6.3/proc/{stat, meminfo, sysrq-trigger} to target/{stat, meminfo, sysrq-trigger} with --
> bind option.
> 
> When a virtual machine to read /proc/meminfo, it will read the meminfo of from 
> userspaces filesystem, we can  get the correct value is returned to the virtual machine 
> from /cgroup/memory.if read /proc/stat, we can get value form /cgroup/cpuacct.
> 
> All mount implemented in lxc_start.c using c language, userspace files can be 
> configured in the configuration file and dynamic loading.
> 
> The function of open and read and write of meminfo,stat,sysrq-trigger must be 
> implemented by us.
> 
> 
> this is a example,in configuration file:
> lxc.cgroup.memory.limit_in_bytes = 268435456
> lxc.cgroup.memory.memsw.limit_in_bytes = 536870912
> 
> [shell]#free -m 
>              total       used       free     shared    buffers     cached
> Mem:           256         13        242          0          0          0
> -/+ buffers/cache:         13        242
> Swap:          512         13        498

Do you have a patch somewhere?

-serge