I have a memory cgroup with 1 process in it.
And look for rss memory usage in that cgroup (in memory.stat) and it is much bigger than rss memory of the process (from /proc/[pid]/status).
The only process pid in cgroup:
$ cat /sys/fs/cgroup/memory/karim/master/cgroup.procs
3744924
The memory limit in cgroup:
$ cat /sys/fs/cgroup/memory/karim/master/memory.limit_in_bytes
7340032000
rss of the cgroup is 990 MB:
$ cat /sys/fs/cgroup/memory/karim/master/memory.stat
cache 5990449152
rss 990224384
rss_huge 0
shmem 0
mapped_file 13516800
dirty 1081344
writeback 270336
pgpgin 4195191
pgpgout 2490628
pgfault 5264589
pgmajfault 0
inactive_anon 0
active_anon 990240768
inactive_file 5862830080
active_file 127021056
unevictable 0
hierarchical_memory_limit 7340032000
total_cache 5990449152
total_rss 990224384
total_rss_huge 0
total_shmem 0
total_mapped_file 13516800
total_dirty 1081344
total_writeback 270336
total_pgpgin 4195191
total_pgpgout 2490628
total_pgfault 5264589
total_pgmajfault 0
total_inactive_anon 0
total_active_anon 990240768
total_inactive_file 5862830080
total_active_file 127021056
total_unevictable 0
rss of the process is 165 MB:
$ cat /proc/3744924/status
Name: [main] /h
Umask: 0002
State: S (sleeping)
Tgid: 3744924
Ngid: 0
Pid: 3744924
PPid: 3744912
TracerPid: 0
Uid: 1000 1000 1000 1000
Gid: 1001 1001 1001 1001
FDSize: 256
Groups: 1000 1001
NStgid: 3744924
NSpid: 3744924
NSpgid: 3744912
NSsid: 45028
VmPeak: 2149068 kB
VmSize: 2088876 kB
VmLck: 0 kB
VmPin: 0 kB
VmHWM: 245352 kB
VmRSS: 198964 kB
RssAnon: 165248 kB
RssFile: 33660 kB
RssShmem: 56 kB
VmData: 575400 kB
VmStk: 132 kB
VmExe: 3048 kB
VmLib: 19180 kB
VmPTE: 1152 kB
VmSwap: 0 kB
HugetlbPages: 0 kB
CoreDumping: 0
THP_enabled: 1
Threads: 17
SigQ: 0/241014
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000001001000
SigCgt: 0000000180000002
CapInh: 0000000000000000
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: 0000003fffffffff
CapAmb: 0000000000000000
NoNewPrivs: 0
Seccomp: 0
Speculation_Store_Bypass: thread vulnerable
Cpus_allowed: fff
Cpus_allowed_list: 0-11
Mems_allowed: 00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000001
Mems_allowed_list: 0
voluntary_ctxt_switches: 94902
nonvoluntary_ctxt_switches: 1903
Why is there such a big difference?