diff options
Diffstat (limited to 'Documentation/cgroups/cgroups.txt')
| -rw-r--r-- | Documentation/cgroups/cgroups.txt | 42 |
1 files changed, 29 insertions, 13 deletions
diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt index d9e5d6f41b92..6eb1a97e88ce 100644 --- a/Documentation/cgroups/cgroups.txt +++ b/Documentation/cgroups/cgroups.txt @@ -56,7 +56,7 @@ hierarchy, and a set of subsystems; each subsystem has system-specific state attached to each cgroup in the hierarchy. Each hierarchy has an instance of the cgroup virtual filesystem associated with it. -At any one time there may be multiple active hierachies of task +At any one time there may be multiple active hierarchies of task cgroups. Each hierarchy is a partition of all tasks in the system. User level code may create and destroy cgroups by name in an @@ -124,10 +124,10 @@ following lines: / \ Prof (15%) students (5%) -Browsers like firefox/lynx go into the WWW network class, while (k)nfsd go +Browsers like Firefox/Lynx go into the WWW network class, while (k)nfsd go into NFS network class. -At the same time firefox/lynx will share an appropriate CPU/Memory class +At the same time Firefox/Lynx will share an appropriate CPU/Memory class depending on who launched it (prof/student). With the ability to classify tasks differently for different resources @@ -252,10 +252,8 @@ cgroup file system directories. When a task is moved from one cgroup to another, it gets a new css_set pointer - if there's an already existing css_set with the desired collection of cgroups then that group is reused, else a new -css_set is allocated. Note that the current implementation uses a -linear search to locate an appropriate existing css_set, so isn't -very efficient. A future version will use a hash table for better -performance. +css_set is allocated. The appropriate existing css_set is located by +looking into a hash table. To allow access from a cgroup to the css_sets (and hence tasks) that comprise it, a set of cg_cgroup_link objects form a lattice; @@ -327,7 +325,7 @@ and then start a subshell 'sh' in that cgroup: Creating, modifying, using the cgroups can be done through the cgroup virtual filesystem. -To mount a cgroup hierarchy will all available subsystems, type: +To mount a cgroup hierarchy with all available subsystems, type: # mount -t cgroup xxx /dev/cgroup The "xxx" is not interpreted by the cgroup code, but will appear in @@ -335,12 +333,23 @@ The "xxx" is not interpreted by the cgroup code, but will appear in To mount a cgroup hierarchy with just the cpuset and numtasks subsystems, type: -# mount -t cgroup -o cpuset,numtasks hier1 /dev/cgroup +# mount -t cgroup -o cpuset,memory hier1 /dev/cgroup To change the set of subsystems bound to a mounted hierarchy, just remount with different options: +# mount -o remount,cpuset,ns hier1 /dev/cgroup -# mount -o remount,cpuset,ns /dev/cgroup +Now memory is removed from the hierarchy and ns is added. + +Note this will add ns to the hierarchy but won't remove memory or +cpuset, because the new options are appended to the old ones: +# mount -o remount,ns /dev/cgroup + +To Specify a hierarchy's release_agent: +# mount -t cgroup -o cpuset,release_agent="/sbin/cpuset_release_agent" \ + xxx /dev/cgroup + +Note that specifying 'release_agent' more than once will return failure. Note that changing the set of subsystems is currently only supported when the hierarchy consists of a single (root) cgroup. Supporting @@ -351,6 +360,11 @@ Then under /dev/cgroup you can find a tree that corresponds to the tree of the cgroups in the system. For instance, /dev/cgroup 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 + +It can also be changed via remount. + If you want to create a new cgroup under /dev/cgroup: # cd /dev/cgroup # mkdir my_cgroup @@ -478,11 +492,13 @@ cgroup->parent is still valid. (Note - can also be called for a newly-created cgroup if an error occurs after this subsystem's create() method has been called for the new cgroup). -void pre_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp); +int pre_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp); Called before checking the reference count on each subsystem. This may be useful for subsystems which have some extra references even if -there are not tasks in the cgroup. +there are not tasks in the cgroup. If pre_destroy() returns error code, +rmdir() will fail with it. From this behavior, pre_destroy() can be +called multiple times against a cgroup. int can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp, struct task_struct *task) @@ -523,7 +539,7 @@ always handled well. 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 paramater +Called at the end of cgroup_clone() 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. |