Task Control Groups: make cpusets a client of cgroups

Portions Copyright (c) 2004-2006 Silicon Graphics, Inc.

Modified by Paul Jackson <pj@sgi.com>

Modified by Christoph Lameter <clameter@sgi.com>

Modified by Paul Menage <menage@google.com>

CONTENTS:

=========

  1.2 Why are cpusets needed ?

  1.3 How are cpusets implemented ?

  1.4 What are exclusive cpusets ?

  1.5 What does notify_on_release do ?

  1.6 What is memory_pressure ?

  1.7 What is memory spread ?

  1.8 How do I use cpusets ?

  1.5 What is memory_pressure ?

  1.6 What is memory spread ?

  1.7 How do I use cpusets ?

2. Usage Examples and Syntax

  2.1 Basic Usage

  2.2 Adding/removing cpus

hooks, beyond what is already present, required to manage dynamic

job placement on large systems.

Each task has a pointer to a cpuset.  Multiple tasks may reference

the same cpuset.  Requests by a task, using the sched_setaffinity(2)

system call to include CPUs in its CPU affinity mask, and using the

mbind(2) and set_mempolicy(2) system calls to include Memory Nodes

in its memory policy, are both filtered through that tasks cpuset,

filtering out any CPUs or Memory Nodes not in that cpuset.  The

scheduler will not schedule a task on a CPU that is not allowed in

its cpus_allowed vector, and the kernel page allocator will not

allocate a page on a node that is not allowed in the requesting tasks

mems_allowed vector.

User level code may create and destroy cpusets by name in the cpuset

Cpusets use the generic cgroup subsystem described in

Documentation/cgroup.txt.

Requests by a task, using the sched_setaffinity(2) system call to

include CPUs in its CPU affinity mask, and using the mbind(2) and

set_mempolicy(2) system calls to include Memory Nodes in its memory

policy, are both filtered through that tasks cpuset, filtering out any

CPUs or Memory Nodes not in that cpuset.  The scheduler will not

schedule a task on a CPU that is not allowed in its cpus_allowed

vector, and the kernel page allocator will not allocate a page on a

node that is not allowed in the requesting tasks mems_allowed vector.

User level code may create and destroy cpusets by name in the cgroup

virtual file system, manage the attributes and permissions of these

cpusets and which CPUs and Memory Nodes are assigned to each cpuset,

specify and query to which cpuset a task is assigned, and list the

 - Cpusets are sets of allowed CPUs and Memory Nodes, known to the

   kernel.

 - Each task in the system is attached to a cpuset, via a pointer

   in the task structure to a reference counted cpuset structure.

   in the task structure to a reference counted cgroup structure.

 - Calls to sched_setaffinity are filtered to just those CPUs

   allowed in that tasks cpuset.

 - Calls to mbind and set_mempolicy are filtered to just

 - in page_alloc.c, to restrict memory to allowed nodes.

 - in vmscan.c, to restrict page recovery to the current cpuset.

In addition a new file system, of type "cpuset" may be mounted,

typically at /dev/cpuset, to enable browsing and modifying the cpusets

presently known to the kernel.  No new system calls are added for

cpusets - all support for querying and modifying cpusets is via

this cpuset file system.

Each task under /proc has an added file named 'cpuset', displaying

the cpuset name, as the path relative to the root of the cpuset file

system.

You should mount the "cgroup" filesystem type in order to enable

browsing and modifying the cpusets presently known to the kernel.  No

new system calls are added for cpusets - all support for querying and

modifying cpusets is via this cpuset file system.

The /proc/<pid>/status file for each task has two added lines,

displaying the tasks cpus_allowed (on which CPUs it may be scheduled)

  Cpus_allowed:   ffffffff,ffffffff,ffffffff,ffffffff

  Mems_allowed:   ffffffff,ffffffff

Each cpuset is represented by a directory in the cpuset file system

containing the following files describing that cpuset:

Each cpuset is represented by a directory in the cgroup file system

containing (on top of the standard cgroup files) the following

files describing that cpuset:

 - cpus: list of CPUs in that cpuset

 - mems: list of Memory Nodes in that cpuset

 - memory_migrate flag: if set, move pages to cpusets nodes

 - cpu_exclusive flag: is cpu placement exclusive?

 - mem_exclusive flag: is memory placement exclusive?

 - tasks: list of tasks (by pid) attached to that cpuset

 - notify_on_release flag: run /sbin/cpuset_release_agent on exit?

 - memory_pressure: measure of how much paging pressure in cpuset

In addition, the root cpuset only has the following file:

outside even a mem_exclusive cpuset.

1.5 What does notify_on_release do ?

------------------------------------

If the notify_on_release flag is enabled (1) in a cpuset, then whenever

the last task in the cpuset leaves (exits or attaches to some other

cpuset) and the last child cpuset of that cpuset is removed, then

the kernel runs the command /sbin/cpuset_release_agent, supplying the

pathname (relative to the mount point of the cpuset file system) of the

abandoned cpuset.  This enables automatic removal of abandoned cpusets.

The default value of notify_on_release in the root cpuset at system

boot is disabled (0).  The default value of other cpusets at creation

is the current value of their parents notify_on_release setting.

1.6 What is memory_pressure ?

1.5 What is memory_pressure ?

-----------------------------

The memory_pressure of a cpuset provides a simple per-cpuset metric

of the rate that the tasks in a cpuset are attempting to free up in

times 1000.

1.7 What is memory spread ?

1.6 What is memory spread ?

---------------------------

There are two boolean flag files per cpuset that control where the

kernel allocates pages for the file system buffers and related in

can become very uneven.

1.8 How do I use cpusets ?

1.7 How do I use cpusets ?

--------------------------

In order to minimize the impact of cpusets on critical kernel

To start a new job that is to be contained within a cpuset, the steps are:

 1) mkdir /dev/cpuset

 2) mount -t cpuset none /dev/cpuset

 2) mount -t cgroup -ocpuset cpuset /dev/cpuset

 3) Create the new cpuset by doing mkdir's and write's (or echo's) in

    the /dev/cpuset virtual file system.

 4) Start a task that will be the "founding father" of the new job.

named "Charlie", containing just CPUs 2 and 3, and Memory Node 1,

and then start a subshell 'sh' in that cpuset:

  mount -t cpuset none /dev/cpuset

  mount -t cgroup -ocpuset cpuset /dev/cpuset

  cd /dev/cpuset

  mkdir Charlie

  cd Charlie

virtual filesystem.

To mount it, type:

# mount -t cpuset none /dev/cpuset

# mount -t cgroup -o cpuset cpuset /dev/cpuset

Then under /dev/cpuset you can find a tree that corresponds to the

tree of the cpusets in the system. For instance, /dev/cpuset

This will fail if the cpuset is in use (has cpusets inside, or has

processes attached).

Note that for legacy reasons, the "cpuset" filesystem exists as a

wrapper around the cgroup filesystem.

The command

mount -t cpuset X /dev/cpuset

is equivalent to

mount -t cgroup -ocpuset X /dev/cpuset

echo "/sbin/cpuset_release_agent" > /dev/cpuset/release_agent

2.2 Adding/removing cpus

------------------------

#ifdef CONFIG_SCHEDSTATS

	INF("schedstat",  S_IRUGO, pid_schedstat),

#endif

#ifdef CONFIG_CPUSETS

#ifdef CONFIG_PROC_PID_CPUSET

	REG("cpuset",     S_IRUGO, cpuset),

#endif

#ifdef CONFIG_CGROUPS

#ifdef CONFIG_SCHEDSTATS

	INF("schedstat", S_IRUGO, pid_schedstat),

#endif

#ifdef CONFIG_CPUSETS

#ifdef CONFIG_PROC_PID_CPUSET

	REG("cpuset",    S_IRUGO, cpuset),

#endif

#ifdef CONFIG_CGROUPS

/* */

#ifdef CONFIG_CPUSETS

SUBSYS(cpuset)

#endif

/* */

/* */

#include <linux/sched.h>

#include <linux/cpumask.h>

#include <linux/nodemask.h>

#include <linux/cgroup.h>

#ifdef CONFIG_CPUSETS

extern int cpuset_init_early(void);

extern int cpuset_init(void);

extern void cpuset_init_smp(void);

extern void cpuset_fork(struct task_struct *p);

extern void cpuset_exit(struct task_struct *p);

extern cpumask_t cpuset_cpus_allowed(struct task_struct *p);

extern nodemask_t cpuset_mems_allowed(struct task_struct *p);

#define cpuset_current_mems_allowed (current->mems_allowed)

extern void cpuset_track_online_nodes(void);

extern int current_cpuset_is_being_rebound(void);

#else /* !CONFIG_CPUSETS */

static inline int cpuset_init_early(void) { return 0; }

static inline int cpuset_init(void) { return 0; }

static inline void cpuset_init_smp(void) {}

static inline void cpuset_fork(struct task_struct *p) {}

static inline void cpuset_exit(struct task_struct *p) {}

static inline cpumask_t cpuset_cpus_allowed(struct task_struct *p)

{

static inline void cpuset_track_online_nodes(void) {}

static inline int current_cpuset_is_being_rebound(void)

{

	return 0;

}

#endif /* !CONFIG_CPUSETS */

#endif /* _LINUX_CPUSET_H */

					const nodemask_t *new);

extern void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new);

extern void mpol_fix_fork_child_flag(struct task_struct *p);

#define set_cpuset_being_rebound(x) (cpuset_being_rebound = (x))

#ifdef CONFIG_CPUSETS

#define current_cpuset_is_being_rebound() \

				(cpuset_being_rebound == current->cpuset)

#else

#define current_cpuset_is_being_rebound() 0

#endif

extern struct mempolicy default_policy;

extern struct zonelist *huge_zonelist(struct vm_area_struct *vma,

int do_migrate_pages(struct mm_struct *mm,

	const nodemask_t *from_nodes, const nodemask_t *to_nodes, int flags);

extern void *cpuset_being_rebound;	/* Trigger mpol_copy vma rebind */

#else

struct mempolicy {};

{

}

#define set_cpuset_being_rebound(x) do {} while (0)

static inline struct zonelist *huge_zonelist(struct vm_area_struct *vma,

 		unsigned long addr, gfp_t gfp_flags, struct mempolicy **mpol)

{