[lxc-devel] [patch 1/1] overwrite /proc/meminfo informations with a fuse

[Serge E. Hallyn]

Quoting Daniel Lezcano (daniel.lezcano at free.fr):
> This patch allows to display information related to the cgroup
> in /proc/meminfo.
> 
> It is a first try, there is certainly a clever way to do that but
> it is just to play with it.
> 
> Compile with:
> 
> 	make lxcfs CFLAGS="-D_FILE_OFFSET_BITS=64 -DFUSE_USE_VERSION=27" LDFLAGS="-lfuse"
> 
> Launch a container as root with:
> 
> 	lxc-execute -n foo /bin/bash
> 
> Set 256MB of memory:
> 
> 	echo 268435456 > /cgroup/foo/memory.limit_in_bytes
> 
> And finally mount /proc/meminfo:
> 
> 	./lxcfs -odirect_io /proc/meminfo
> 
> And the results are:
> 
> cat /proc/meminfo:
> ==================
> 
> MemTotal:      262144 kB
> MemFree:       255991 kB
> 
> top:
> ====
> 
> top - 23:52:17 up  2:43,  2 users,  load average: 0.00, 0.00, 0.00
> Tasks:   6 total,   1 running,   5 sleeping,   0 stopped,   0 zombie
> Cpu(s):  0.0%us,  0.3%sy,  0.0%ni, 99.0%id,  0.0%wa,  0.0%hi,  0.7%si,  0.0
> Mem:    262144k total,     6153k used,   255991k free,        0k buffers
> Swap:        0k total,        0k used,        0k free,        0k cached
> 
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND       
>     1 dlezcano  20   0  8136  484  408 S  0.0  0.2   0:00.00 lxc-init      
>     2 dlezcano  20   0 90112 1764 1304 S  0.0  0.7   0:00.08 bash          
>    29 root      20   0  121m 1392 1128 S  0.0  0.5   0:00.05 su            
>    30 root      20   0 89984 1696 1328 S  0.0  0.6   0:00.05 bash          
>    68 root      20   0 37628  888  544 S  0.0  0.3   0:00.00 lxcfs         
>    74 root      20   0 14748 1040  868 R  0.0  0.4   0:00.02 top           
> 
> free:
> =====
> 
>              total       used       free     shared    buffers     cached
> Mem:        262144       6153     255991          0          0          0
> -/+ buffers/cache:       6153     255991
> 
> 
> To be extended ...

Thanks, Daniel.  This looks cool, and a generic config-driven one
would rock.  I've looked through it a bit but am afraid I can't
do it justice without knowing more about the fuse libs (i.e. don't
know when lxcfs_destroy() can get called, or if private_data
can be not- or partially-instantiated...)

I saw no obvious problems though.

Now here's a question...  Do we care to muck around with contents
of /proc/self/xyz too?  I.e. /proc/self/mountinfo inside a container
could have 30 lines, of which only 5 are relaly relevant to the
container.  I'm not sure there is a sane way to pare those down
though...

thanks,
-serge