the admin can easily set up a script which receives exec notifications
and depending on who is launching the browser he can
- # echo browser_pid > /mnt/<restype>/<userclass>/tasks
+ # echo browser_pid > /sys/fs/cgroup/<restype>/<userclass>/tasks
With only a single hierarchy, he now would potentially have to create
a separate cgroup for every browser launched and associate it with
-approp network and other resource class. This may lead to
+appropriate network and other resource class. This may lead to
proliferation of such cgroups.
Also lets say that the administrator would like to give enhanced network
With ability to write pids directly to resource classes, it's just a
matter of :
- # echo pid > /mnt/network/<new_class>/tasks
+ # echo pid > /sys/fs/cgroup/network/<new_class>/tasks
(after some time)
- # echo pid > /mnt/network/<orig_class>/tasks
+ # echo pid > /sys/fs/cgroup/network/<orig_class>/tasks
Without this ability, he would have to split the cgroup into
multiple separate ones and then associate the new cgroups with the
- cgroup.procs: list of tgids in the cgroup. This list is not
guaranteed to be sorted or free of duplicate tgids, and userspace
should sort/uniquify the list if this property is required.
- This is a read-only file, for now.
+ Writing a thread group id into this file moves all threads in that
+ group into this cgroup.
- notify_on_release flag: run the release agent on exit?
- release_agent: the path to use for release notifications (this file
exists in the top cgroup only)
To start a new job that is to be contained within a cgroup, using
the "cpuset" cgroup subsystem, the steps are something like:
- 1) mkdir /dev/cgroup
- 2) mount -t cgroup -ocpuset cpuset /dev/cgroup
- 3) Create the new cgroup by doing mkdir's and write's (or echo's) in
- the /dev/cgroup virtual file system.
- 4) Start a task that will be the "founding father" of the new job.
- 5) Attach that task to the new cgroup by writing its pid to the
- /dev/cgroup tasks file for that cgroup.
- 6) fork, exec or clone the job tasks from this founding father task.
+ 1) mount -t tmpfs cgroup_root /sys/fs/cgroup
+ 2) mkdir /sys/fs/cgroup/cpuset
+ 3) mount -t cgroup -ocpuset cpuset /sys/fs/cgroup/cpuset
+ 4) Create the new cgroup by doing mkdir's and write's (or echo's) in
+ the /sys/fs/cgroup virtual file system.
+ 5) Start a task that will be the "founding father" of the new job.
+ 6) Attach that task to the new cgroup by writing its pid to the
+ /sys/fs/cgroup/cpuset/tasks file for that cgroup.
+ 7) fork, exec or clone the job tasks from this founding father task.
For example, the following sequence of commands will setup a cgroup
named "Charlie", containing just CPUs 2 and 3, and Memory Node 1,
and then start a subshell 'sh' in that cgroup:
- mount -t cgroup cpuset -ocpuset /dev/cgroup
- cd /dev/cgroup
+ mount -t tmpfs cgroup_root /sys/fs/cgroup
+ mkdir /sys/fs/cgroup/cpuset
+ mount -t cgroup cpuset -ocpuset /sys/fs/cgroup/cpuset
+ cd /sys/fs/cgroup/cpuset
mkdir Charlie
cd Charlie
/bin/echo 2-3 > cpuset.cpus
virtual filesystem.
To mount a cgroup hierarchy with all available subsystems, type:
-# mount -t cgroup xxx /dev/cgroup
+# mount -t cgroup xxx /sys/fs/cgroup
The "xxx" is not interpreted by the cgroup code, but will appear in
/proc/mounts so may be any useful identifying string that you like.
if cpusets are enabled the user will have to populate the cpus and mems files
for each new cgroup created before that group can be used.
+As explained in section `1.2 Why are cgroups needed?' you should create
+different hierarchies of cgroups for each single resource or group of
+resources you want to control. Therefore, you should mount a tmpfs on
+/sys/fs/cgroup and create directories for each cgroup resource or resource
+group.
+
+# mount -t tmpfs cgroup_root /sys/fs/cgroup
+# mkdir /sys/fs/cgroup/rg1
+
To mount a cgroup hierarchy with just the cpuset and memory
subsystems, type:
-# mount -t cgroup -o cpuset,memory hier1 /dev/cgroup
+# mount -t cgroup -o cpuset,memory hier1 /sys/fs/cgroup/rg1
To change the set of subsystems bound to a mounted hierarchy, just
remount with different options:
-# mount -o remount,cpuset,blkio hier1 /dev/cgroup
+# mount -o remount,cpuset,blkio hier1 /sys/fs/cgroup/rg1
Now memory is removed from the hierarchy and blkio is added.
Note this will add blkio to the hierarchy but won't remove memory or
cpuset, because the new options are appended to the old ones:
-# mount -o remount,blkio /dev/cgroup
+# mount -o remount,blkio /sys/fs/cgroup/rg1
To Specify a hierarchy's release_agent:
# mount -t cgroup -o cpuset,release_agent="/sbin/cpuset_release_agent" \
- xxx /dev/cgroup
+ xxx /sys/fs/cgroup/rg1
Note that specifying 'release_agent' more than once will return failure.
the ability to arbitrarily bind/unbind subsystems from an existing
cgroup hierarchy is intended to be implemented in the future.
-Then under /dev/cgroup you can find a tree that corresponds to the
-tree of the cgroups in the system. For instance, /dev/cgroup
+Then under /sys/fs/cgroup/rg1 you can find a tree that corresponds to the
+tree of the cgroups in the system. For instance, /sys/fs/cgroup/rg1
is the cgroup that holds the whole system.
If you want to change the value of release_agent:
-# echo "/sbin/new_release_agent" > /dev/cgroup/release_agent
+# echo "/sbin/new_release_agent" > /sys/fs/cgroup/rg1/release_agent
It can also be changed via remount.
-If you want to create a new cgroup under /dev/cgroup:
-# cd /dev/cgroup
+If you want to create a new cgroup under /sys/fs/cgroup/rg1:
+# cd /sys/fs/cgroup/rg1
# mkdir my_cgroup
Now you want to do something with this cgroup.
# echo 0 > tasks
+You can use the cgroup.procs file instead of the tasks file to move all
+threads in a threadgroup at once. Echoing the pid of any task in a
+threadgroup to cgroup.procs causes all tasks in that threadgroup to be
+be attached to the cgroup. Writing 0 to cgroup.procs moves all tasks
+in the writing task's threadgroup.
+
Note: Since every task is always a member of exactly one cgroup in each
mounted hierarchy, to remove a task from its current cgroup you must
move it into a new cgroup (possibly the root cgroup) by writing to the
called multiple times against a cgroup.
int can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
- struct task_struct *task, bool threadgroup)
+ struct task_struct *task)
(cgroup_mutex held by caller)
Called prior to moving a task into a cgroup; if the subsystem
unspecified task can be moved into the cgroup. Note that this isn't
called on a fork. If this method returns 0 (success) then this should
remain valid while the caller holds cgroup_mutex and it is ensured that either
-attach() or cancel_attach() will be called in future. If threadgroup is
-true, then a successful result indicates that all threads in the given
-thread's threadgroup can be moved together.
+attach() or cancel_attach() will be called in future.
+
+int can_attach_task(struct cgroup *cgrp, struct task_struct *tsk);
+(cgroup_mutex held by caller)
+
+As can_attach, but for operations that must be run once per task to be
+attached (possibly many when using cgroup_attach_proc). Called after
+can_attach.
void cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *task, bool threadgroup)
This will be called only about subsystems whose can_attach() operation have
succeeded.
+void pre_attach(struct cgroup *cgrp);
+(cgroup_mutex held by caller)
+
+For any non-per-thread attachment work that needs to happen before
+attach_task. Needed by cpuset.
+
void attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
- struct cgroup *old_cgrp, struct task_struct *task,
- bool threadgroup)
+ struct cgroup *old_cgrp, struct task_struct *task)
(cgroup_mutex held by caller)
Called after the task has been attached to the cgroup, to allow any
post-attachment activity that requires memory allocations or blocking.
-If threadgroup is true, the subsystem should take care of all threads
-in the specified thread's threadgroup. Currently does not support any
+
+void attach_task(struct cgroup *cgrp, struct task_struct *tsk);
+(cgroup_mutex held by caller)
+
+As attach, but for operations that must be run once per task to be attached,
+like can_attach_task. Called before attach. Currently does not support any
subsystem that might need the old_cgrp for every thread in the group.
void fork(struct cgroup_subsy *ss, struct task_struct *task)
void post_clone(struct cgroup_subsys *ss, struct cgroup *cgrp)
(cgroup_mutex held by caller)
-Called at the end of cgroup_clone() to do any parameter
+Called during cgroup_create() to do any parameter
initialization which might be required before a task could attach. For
example in cpusets, no task may attach before 'cpus' and 'mems' are set
up.
projects / firefly-linux-kernel-4.4.55.git / blobdiff