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Is a cgroup a list of key value pairs or a set of processes?

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-1

I get the idea that a cgroup is a set of processes satisfying some conditions, from http://man7.org/linux/man-pages/man7/cgroups.7.html

A cgroup is a collection of processes that are bound to a set of
limits or parameters defined via the cgroup filesystem.

Am I correct that to find out the cgroup of a process with a givn PID, just run

$ cat /proc/11/cgroup
12:perf_event:/
11:blkio:/
10:hugetlb:/
9:freezer:/
8:pids:/
7:cpuset:/
6:devices:/
5:cpu,cpuacct:/
4:rdma:/
3:memory:/
2:net_cls,net_prio:/
1:name=systemd:/
0::/

I thought cgroup is a id number. but it is a list of key value pairs.
Does the above list of key value pairs represent a list of processes?

Can I find out all the processes in the same cgroup?

Thanks.

cgroups

share|improve this question

edited Apr 5 at 18:27

Stephen Kitt

180k25411491

asked Apr 5 at 17:52

TimTim

28.5k79269491

add a comment | 

-1

I get the idea that a cgroup is a set of processes satisfying some conditions, from http://man7.org/linux/man-pages/man7/cgroups.7.html

A cgroup is a collection of processes that are bound to a set of
limits or parameters defined via the cgroup filesystem.

Am I correct that to find out the cgroup of a process with a givn PID, just run

$ cat /proc/11/cgroup
12:perf_event:/
11:blkio:/
10:hugetlb:/
9:freezer:/
8:pids:/
7:cpuset:/
6:devices:/
5:cpu,cpuacct:/
4:rdma:/
3:memory:/
2:net_cls,net_prio:/
1:name=systemd:/
0::/

I thought cgroup is a id number. but it is a list of key value pairs.
Does the above list of key value pairs represent a list of processes?

Can I find out all the processes in the same cgroup?

Thanks.

cgroups

share|improve this question

edited Apr 5 at 18:27

Stephen Kitt

180k25411491

asked Apr 5 at 17:52

TimTim

28.5k79269491

add a comment | 

I get the idea that a cgroup is a set of processes satisfying some conditions, from http://man7.org/linux/man-pages/man7/cgroups.7.html

A cgroup is a collection of processes that are bound to a set of
limits or parameters defined via the cgroup filesystem.

Am I correct that to find out the cgroup of a process with a givn PID, just run

$ cat /proc/11/cgroup
12:perf_event:/
11:blkio:/
10:hugetlb:/
9:freezer:/
8:pids:/
7:cpuset:/
6:devices:/
5:cpu,cpuacct:/
4:rdma:/
3:memory:/
2:net_cls,net_prio:/
1:name=systemd:/
0::/

I thought cgroup is a id number. but it is a list of key value pairs.
Does the above list of key value pairs represent a list of processes?

Can I find out all the processes in the same cgroup?

Thanks.

cgroups

share|improve this question

edited Apr 5 at 18:27

Stephen Kitt

180k25411491

asked Apr 5 at 17:52

TimTim

28.5k79269491

$ cat /proc/11/cgroup
12:perf_event:/
11:blkio:/
10:hugetlb:/
9:freezer:/
8:pids:/
7:cpuset:/
6:devices:/
5:cpu,cpuacct:/
4:rdma:/
3:memory:/
2:net_cls,net_prio:/
1:name=systemd:/
0::/

share|improve this question

edited Apr 5 at 18:27

Stephen Kitt

180k25411491

asked Apr 5 at 17:52

TimTim

28.5k79269491

share|improve this question

edited Apr 5 at 18:27

Stephen Kitt

180k25411491

asked Apr 5 at 17:52

TimTim

28.5k79269491

edited Apr 5 at 18:27

Stephen Kitt

180k25411491

edited Apr 5 at 18:27

Stephen Kitt

180k25411491

asked Apr 5 at 17:52

TimTim

28.5k79269491

asked Apr 5 at 17:52

TimTim

28.5k79269491

1 Answer
1

active

oldest

votes

2

As indicated in the manual page you’re referring to, a cgroup is a set of processes.

The contents of /proc/11/cgroup describe all the control groups to which process 11 belongs. For v1 groups, the first field on each line is the hierarchy id, the second is the list of controllers, and the third is the pathname of the cgroup in the hierarchy. For v2 groups, the first field is 0, the second is empty, and the third is the pathname.

To find all the processes in a cgroup, look at the tasks file in the corresponding sysfs directory, for example

cat /sys/fs/cgroup/perf_event/tasks

which corresponds to 12:perf_event:/:

| /sys/fs/cgroup/ | perf_event | / | tasks
| | | |
|< mountpoint >|<controller>| ^ |
 |
 cgroup pathname --+

share|improve this answer

edited yesterday

answered Apr 5 at 18:37

Stephen KittStephen Kitt

180k25411491

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. perf_event isn't a cgroup but a controller. So /sys/fs/cgroup/perf_event/tasks seems to find all processes for a controller
  
  – Tim
  Apr 5 at 23:44
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You’re forgetting the third field in 12:perf_event:/.
  
  – Stephen Kitt
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  (1) The third field is "the pathname of the cgroup in the hierarchy", here /. Is it a relative pathname with respect to some other pathname? (2) Does /sys/fs/cgroup/perf_event/tasks depend on the third field? also on the second field, which is a list of controllers?
  
  – Tim
  yesterday
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I posted a related post unix.stackexchange.com/questions/511066/…
  
  – Tim
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You really don’t see how /sys/fs/cgroup/perf_event/tasks is contructed, based on the information in 12:perf_event:/?
  
  – Stephen Kitt
  yesterday
  

  
  
  
  

 | 
show 4 more comments

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2

As indicated in the manual page you’re referring to, a cgroup is a set of processes.

The contents of /proc/11/cgroup describe all the control groups to which process 11 belongs. For v1 groups, the first field on each line is the hierarchy id, the second is the list of controllers, and the third is the pathname of the cgroup in the hierarchy. For v2 groups, the first field is 0, the second is empty, and the third is the pathname.

To find all the processes in a cgroup, look at the tasks file in the corresponding sysfs directory, for example

cat /sys/fs/cgroup/perf_event/tasks

which corresponds to 12:perf_event:/:

| /sys/fs/cgroup/ | perf_event | / | tasks
| | | |
|< mountpoint >|<controller>| ^ |
 |
 cgroup pathname --+

share|improve this answer

edited yesterday

answered Apr 5 at 18:37

Stephen KittStephen Kitt

180k25411491

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. perf_event isn't a cgroup but a controller. So /sys/fs/cgroup/perf_event/tasks seems to find all processes for a controller
  
  – Tim
  Apr 5 at 23:44
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You’re forgetting the third field in 12:perf_event:/.
  
  – Stephen Kitt
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  (1) The third field is "the pathname of the cgroup in the hierarchy", here /. Is it a relative pathname with respect to some other pathname? (2) Does /sys/fs/cgroup/perf_event/tasks depend on the third field? also on the second field, which is a list of controllers?
  
  – Tim
  yesterday
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I posted a related post unix.stackexchange.com/questions/511066/…
  
  – Tim
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You really don’t see how /sys/fs/cgroup/perf_event/tasks is contructed, based on the information in 12:perf_event:/?
  
  – Stephen Kitt
  yesterday
  

  
  
  
  

 | 
show 4 more comments

2

As indicated in the manual page you’re referring to, a cgroup is a set of processes.

The contents of /proc/11/cgroup describe all the control groups to which process 11 belongs. For v1 groups, the first field on each line is the hierarchy id, the second is the list of controllers, and the third is the pathname of the cgroup in the hierarchy. For v2 groups, the first field is 0, the second is empty, and the third is the pathname.

To find all the processes in a cgroup, look at the tasks file in the corresponding sysfs directory, for example

cat /sys/fs/cgroup/perf_event/tasks

which corresponds to 12:perf_event:/:

| /sys/fs/cgroup/ | perf_event | / | tasks
| | | |
|< mountpoint >|<controller>| ^ |
 |
 cgroup pathname --+

share|improve this answer

edited yesterday

answered Apr 5 at 18:37

Stephen KittStephen Kitt

180k25411491

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. perf_event isn't a cgroup but a controller. So /sys/fs/cgroup/perf_event/tasks seems to find all processes for a controller
  
  – Tim
  Apr 5 at 23:44
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You’re forgetting the third field in 12:perf_event:/.
  
  – Stephen Kitt
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  (1) The third field is "the pathname of the cgroup in the hierarchy", here /. Is it a relative pathname with respect to some other pathname? (2) Does /sys/fs/cgroup/perf_event/tasks depend on the third field? also on the second field, which is a list of controllers?
  
  – Tim
  yesterday
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I posted a related post unix.stackexchange.com/questions/511066/…
  
  – Tim
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You really don’t see how /sys/fs/cgroup/perf_event/tasks is contructed, based on the information in 12:perf_event:/?
  
  – Stephen Kitt
  yesterday
  

  
  
  
  

 | 
show 4 more comments

As indicated in the manual page you’re referring to, a cgroup is a set of processes.

The contents of /proc/11/cgroup describe all the control groups to which process 11 belongs. For v1 groups, the first field on each line is the hierarchy id, the second is the list of controllers, and the third is the pathname of the cgroup in the hierarchy. For v2 groups, the first field is 0, the second is empty, and the third is the pathname.

To find all the processes in a cgroup, look at the tasks file in the corresponding sysfs directory, for example

cat /sys/fs/cgroup/perf_event/tasks

which corresponds to 12:perf_event:/:

| /sys/fs/cgroup/ | perf_event | / | tasks
| | | |
|< mountpoint >|<controller>| ^ |
 |
 cgroup pathname --+

share|improve this answer

edited yesterday

answered Apr 5 at 18:37

Stephen KittStephen Kitt

180k25411491

cat /sys/fs/cgroup/perf_event/tasks

| /sys/fs/cgroup/ | perf_event | / | tasks
| | | |
|< mountpoint >|<controller>| ^ |
 |
 cgroup pathname --+

share|improve this answer

edited yesterday

answered Apr 5 at 18:37

Stephen KittStephen Kitt

180k25411491

answered Apr 5 at 18:37

Stephen KittStephen Kitt

180k25411491

answered Apr 5 at 18:37

Stephen KittStephen Kitt

180k25411491