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linux/kernel/cpuset.c

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/*
* kernel/cpuset.c
*
* Processor and Memory placement constraints for sets of tasks.
*
* Copyright (C) 2003 BULL SA.
* Copyright (C) 2004-2007 Silicon Graphics, Inc.
* Copyright (C) 2006 Google, Inc
*
* Portions derived from Patrick Mochel's sysfs code.
* sysfs is Copyright (c) 2001-3 Patrick Mochel
*
* 2003-10-10 Written by Simon Derr.
* 2003-10-22 Updates by Stephen Hemminger.
* 2004 May-July Rework by Paul Jackson.
* 2006 Rework by Paul Menage to use generic cgroups
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of the Linux
* distribution for more details.
*/
#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/cpuset.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/list.h>
#include <linux/mempolicy.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/pagemap.h>
#include <linux/prio_heap.h>
#include <linux/proc_fs.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/time.h>
#include <linux/backing-dev.h>
#include <linux/sort.h>
#include <asm/uaccess.h>
#include <asm/atomic.h>
#include <linux/mutex.h>
#include <linux/kfifo.h>
/*
* Tracks how many cpusets are currently defined in system.
* When there is only one cpuset (the root cpuset) we can
* short circuit some hooks.
*/
int number_of_cpusets __read_mostly;
/* Retrieve the cpuset from a cgroup */
struct cgroup_subsys cpuset_subsys;
struct cpuset;
/* See "Frequency meter" comments, below. */
struct fmeter {
int cnt; /* unprocessed events count */
int val; /* most recent output value */
time_t time; /* clock (secs) when val computed */
spinlock_t lock; /* guards read or write of above */
};
struct cpuset {
struct cgroup_subsys_state css;
unsigned long flags; /* "unsigned long" so bitops work */
cpumask_t cpus_allowed; /* CPUs allowed to tasks in cpuset */
nodemask_t mems_allowed; /* Memory Nodes allowed to tasks */
struct cpuset *parent; /* my parent */
/*
* Copy of global cpuset_mems_generation as of the most
* recent time this cpuset changed its mems_allowed.
*/
int mems_generation;
struct fmeter fmeter; /* memory_pressure filter */
/* partition number for rebuild_sched_domains() */
int pn;
};
/* Retrieve the cpuset for a cgroup */
static inline struct cpuset *cgroup_cs(struct cgroup *cont)
{
return container_of(cgroup_subsys_state(cont, cpuset_subsys_id),
struct cpuset, css);
}
/* Retrieve the cpuset for a task */
static inline struct cpuset *task_cs(struct task_struct *task)
{
return container_of(task_subsys_state(task, cpuset_subsys_id),
struct cpuset, css);
}
/* bits in struct cpuset flags field */
typedef enum {
CS_CPU_EXCLUSIVE,
CS_MEM_EXCLUSIVE,
CS_MEMORY_MIGRATE,
CS_SCHED_LOAD_BALANCE,
CS_SPREAD_PAGE,
CS_SPREAD_SLAB,
} cpuset_flagbits_t;
/* convenient tests for these bits */
static inline int is_cpu_exclusive(const struct cpuset *cs)
{
return test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
}
static inline int is_mem_exclusive(const struct cpuset *cs)
{
return test_bit(CS_MEM_EXCLUSIVE, &cs->flags);
}
static inline int is_sched_load_balance(const struct cpuset *cs)
{
return test_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
}
static inline int is_memory_migrate(const struct cpuset *cs)
{
return test_bit(CS_MEMORY_MIGRATE, &cs->flags);
}
static inline int is_spread_page(const struct cpuset *cs)
{
return test_bit(CS_SPREAD_PAGE, &cs->flags);
}
static inline int is_spread_slab(const struct cpuset *cs)
{
return test_bit(CS_SPREAD_SLAB, &cs->flags);
}
/*
* Increment this integer everytime any cpuset changes its
* mems_allowed value. Users of cpusets can track this generation
* number, and avoid having to lock and reload mems_allowed unless
* the cpuset they're using changes generation.
*
* A single, global generation is needed because attach_task() could
* reattach a task to a different cpuset, which must not have its
* generation numbers aliased with those of that tasks previous cpuset.
*
* Generations are needed for mems_allowed because one task cannot
* modify anothers memory placement. So we must enable every task,
* on every visit to __alloc_pages(), to efficiently check whether
* its current->cpuset->mems_allowed has changed, requiring an update
* of its current->mems_allowed.
*
* Since cpuset_mems_generation is guarded by manage_mutex,
* there is no need to mark it atomic.
*/
static int cpuset_mems_generation;
static struct cpuset top_cpuset = {
.flags = ((1 << CS_CPU_EXCLUSIVE) | (1 << CS_MEM_EXCLUSIVE)),
.cpus_allowed = CPU_MASK_ALL,
.mems_allowed = NODE_MASK_ALL,
};
/*
* We have two global cpuset mutexes below. They can nest.
* It is ok to first take manage_mutex, then nest callback_mutex. We also
* require taking task_lock() when dereferencing a tasks cpuset pointer.
* See "The task_lock() exception", at the end of this comment.
*
* A task must hold both mutexes to modify cpusets. If a task
* holds manage_mutex, then it blocks others wanting that mutex,
* ensuring that it is the only task able to also acquire callback_mutex
* and be able to modify cpusets. It can perform various checks on
* the cpuset structure first, knowing nothing will change. It can
* also allocate memory while just holding manage_mutex. While it is
* performing these checks, various callback routines can briefly
* acquire callback_mutex to query cpusets. Once it is ready to make
* the changes, it takes callback_mutex, blocking everyone else.
*
* Calls to the kernel memory allocator can not be made while holding
* callback_mutex, as that would risk double tripping on callback_mutex
* from one of the callbacks into the cpuset code from within
* __alloc_pages().
*
* If a task is only holding callback_mutex, then it has read-only
* access to cpusets.
*
* The task_struct fields mems_allowed and mems_generation may only
* be accessed in the context of that task, so require no locks.
*
* Any task can increment and decrement the count field without lock.
* So in general, code holding manage_mutex or callback_mutex can't rely
* on the count field not changing. However, if the count goes to
* zero, then only attach_task(), which holds both mutexes, can
* increment it again. Because a count of zero means that no tasks
* are currently attached, therefore there is no way a task attached
* to that cpuset can fork (the other way to increment the count).
* So code holding manage_mutex or callback_mutex can safely assume that
* if the count is zero, it will stay zero. Similarly, if a task
* holds manage_mutex or callback_mutex on a cpuset with zero count, it
* knows that the cpuset won't be removed, as cpuset_rmdir() needs
* both of those mutexes.
*
* The cpuset_common_file_write handler for operations that modify
* the cpuset hierarchy holds manage_mutex across the entire operation,
* single threading all such cpuset modifications across the system.
*
* The cpuset_common_file_read() handlers only hold callback_mutex across
* small pieces of code, such as when reading out possibly multi-word
* cpumasks and nodemasks.
*
* The fork and exit callbacks cpuset_fork() and cpuset_exit(), don't
* (usually) take either mutex. These are the two most performance
* critical pieces of code here. The exception occurs on cpuset_exit(),
* when a task in a notify_on_release cpuset exits. Then manage_mutex
* is taken, and if the cpuset count is zero, a usermode call made
* to /sbin/cpuset_release_agent with the name of the cpuset (path
* relative to the root of cpuset file system) as the argument.
*
* A cpuset can only be deleted if both its 'count' of using tasks
* is zero, and its list of 'children' cpusets is empty. Since all
* tasks in the system use _some_ cpuset, and since there is always at
* least one task in the system (init), therefore, top_cpuset
* always has either children cpusets and/or using tasks. So we don't
* need a special hack to ensure that top_cpuset cannot be deleted.
*
* The above "Tale of Two Semaphores" would be complete, but for:
*
* The task_lock() exception
*
* The need for this exception arises from the action of attach_task(),
* which overwrites one tasks cpuset pointer with another. It does
* so using both mutexes, however there are several performance
* critical places that need to reference task->cpuset without the
* expense of grabbing a system global mutex. Therefore except as
* noted below, when dereferencing or, as in attach_task(), modifying
* a tasks cpuset pointer we use task_lock(), which acts on a spinlock
* (task->alloc_lock) already in the task_struct routinely used for
* such matters.
*
* P.S. One more locking exception. RCU is used to guard the
* update of a tasks cpuset pointer by attach_task() and the
* access of task->cpuset->mems_generation via that pointer in
* the routine cpuset_update_task_memory_state().
*/
static DEFINE_MUTEX(callback_mutex);
/* This is ugly, but preserves the userspace API for existing cpuset
* users. If someone tries to mount the "cpuset" filesystem, we
* silently switch it to mount "cgroup" instead */
static int cpuset_get_sb(struct file_system_type *fs_type,
int flags, const char *unused_dev_name,
void *data, struct vfsmount *mnt)
{
struct file_system_type *cgroup_fs = get_fs_type("cgroup");
int ret = -ENODEV;
if (cgroup_fs) {
char mountopts[] =
"cpuset,noprefix,"
"release_agent=/sbin/cpuset_release_agent";
ret = cgroup_fs->get_sb(cgroup_fs, flags,
unused_dev_name, mountopts, mnt);
put_filesystem(cgroup_fs);
}
return ret;
}
static struct file_system_type cpuset_fs_type = {
.name = "cpuset",
.get_sb = cpuset_get_sb,
};
/*
* Return in *pmask the portion of a cpusets's cpus_allowed that
* are online. If none are online, walk up the cpuset hierarchy
* until we find one that does have some online cpus. If we get
* all the way to the top and still haven't found any online cpus,
* return cpu_online_map. Or if passed a NULL cs from an exit'ing
* task, return cpu_online_map.
*
* One way or another, we guarantee to return some non-empty subset
* of cpu_online_map.
*
* Call with callback_mutex held.
*/
static void guarantee_online_cpus(const struct cpuset *cs, cpumask_t *pmask)
{
while (cs && !cpus_intersects(cs->cpus_allowed, cpu_online_map))
cs = cs->parent;
if (cs)
cpus_and(*pmask, cs->cpus_allowed, cpu_online_map);
else
*pmask = cpu_online_map;
BUG_ON(!cpus_intersects(*pmask, cpu_online_map));
}
/*
* Return in *pmask the portion of a cpusets's mems_allowed that
* are online, with memory. If none are online with memory, walk
* up the cpuset hierarchy until we find one that does have some
* online mems. If we get all the way to the top and still haven't
* found any online mems, return node_states[N_HIGH_MEMORY].
*
* One way or another, we guarantee to return some non-empty subset
* of node_states[N_HIGH_MEMORY].
*
* Call with callback_mutex held.
*/
static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
{
while (cs && !nodes_intersects(cs->mems_allowed,
node_states[N_HIGH_MEMORY]))
cs = cs->parent;
if (cs)
nodes_and(*pmask, cs->mems_allowed,
node_states[N_HIGH_MEMORY]);
else
*pmask = node_states[N_HIGH_MEMORY];
BUG_ON(!nodes_intersects(*pmask, node_states[N_HIGH_MEMORY]));
}
/**
* cpuset_update_task_memory_state - update task memory placement
*
* If the current tasks cpusets mems_allowed changed behind our
* backs, update current->mems_allowed, mems_generation and task NUMA
* mempolicy to the new value.
*
* Task mempolicy is updated by rebinding it relative to the
* current->cpuset if a task has its memory placement changed.
* Do not call this routine if in_interrupt().
*
* Call without callback_mutex or task_lock() held. May be
* called with or without manage_mutex held. Thanks in part to
* 'the_top_cpuset_hack', the tasks cpuset pointer will never
* be NULL. This routine also might acquire callback_mutex and
* current->mm->mmap_sem during call.
*
* Reading current->cpuset->mems_generation doesn't need task_lock
* to guard the current->cpuset derefence, because it is guarded
* from concurrent freeing of current->cpuset by attach_task(),
* using RCU.
*
* The rcu_dereference() is technically probably not needed,
* as I don't actually mind if I see a new cpuset pointer but
* an old value of mems_generation. However this really only
* matters on alpha systems using cpusets heavily. If I dropped
* that rcu_dereference(), it would save them a memory barrier.
* For all other arch's, rcu_dereference is a no-op anyway, and for
* alpha systems not using cpusets, another planned optimization,
* avoiding the rcu critical section for tasks in the root cpuset
* which is statically allocated, so can't vanish, will make this
* irrelevant. Better to use RCU as intended, than to engage in
* some cute trick to save a memory barrier that is impossible to
* test, for alpha systems using cpusets heavily, which might not
* even exist.
*
* This routine is needed to update the per-task mems_allowed data,
* within the tasks context, when it is trying to allocate memory
* (in various mm/mempolicy.c routines) and notices that some other
* task has been modifying its cpuset.
*/
void cpuset_update_task_memory_state(void)
{
int my_cpusets_mem_gen;
struct task_struct *tsk = current;
struct cpuset *cs;
if (task_cs(tsk) == &top_cpuset) {
/* Don't need rcu for top_cpuset. It's never freed. */
my_cpusets_mem_gen = top_cpuset.mems_generation;
} else {
rcu_read_lock();
my_cpusets_mem_gen = task_cs(current)->mems_generation;
rcu_read_unlock();
}
if (my_cpusets_mem_gen != tsk->cpuset_mems_generation) {
mutex_lock(&callback_mutex);
task_lock(tsk);
cs = task_cs(tsk); /* Maybe changed when task not locked */
guarantee_online_mems(cs, &tsk->mems_allowed);
tsk->cpuset_mems_generation = cs->mems_generation;
if (is_spread_page(cs))
tsk->flags |= PF_SPREAD_PAGE;
else
tsk->flags &= ~PF_SPREAD_PAGE;
if (is_spread_slab(cs))
tsk->flags |= PF_SPREAD_SLAB;
else
tsk->flags &= ~PF_SPREAD_SLAB;
task_unlock(tsk);
mutex_unlock(&callback_mutex);
mpol_rebind_task(tsk, &tsk->mems_allowed);
}
}
/*
* is_cpuset_subset(p, q) - Is cpuset p a subset of cpuset q?
*
* One cpuset is a subset of another if all its allowed CPUs and
* Memory Nodes are a subset of the other, and its exclusive flags
* are only set if the other's are set. Call holding manage_mutex.
*/
static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
{
return cpus_subset(p->cpus_allowed, q->cpus_allowed) &&
nodes_subset(p->mems_allowed, q->mems_allowed) &&
is_cpu_exclusive(p) <= is_cpu_exclusive(q) &&
is_mem_exclusive(p) <= is_mem_exclusive(q);
}
/*
* validate_change() - Used to validate that any proposed cpuset change
* follows the structural rules for cpusets.
*
* If we replaced the flag and mask values of the current cpuset
* (cur) with those values in the trial cpuset (trial), would
* our various subset and exclusive rules still be valid? Presumes
* manage_mutex held.
*
* 'cur' is the address of an actual, in-use cpuset. Operations
* such as list traversal that depend on the actual address of the
* cpuset in the list must use cur below, not trial.
*
* 'trial' is the address of bulk structure copy of cur, with
* perhaps one or more of the fields cpus_allowed, mems_allowed,
* or flags changed to new, trial values.
*
* Return 0 if valid, -errno if not.
*/
static int validate_change(const struct cpuset *cur, const struct cpuset *trial)
{
struct cgroup *cont;
struct cpuset *c, *par;
/* Each of our child cpusets must be a subset of us */
list_for_each_entry(cont, &cur->css.cgroup->children, sibling) {
if (!is_cpuset_subset(cgroup_cs(cont), trial))
return -EBUSY;
}
/* Remaining checks don't apply to root cpuset */
if (cur == &top_cpuset)
return 0;
par = cur->parent;
/* We must be a subset of our parent cpuset */
if (!is_cpuset_subset(trial, par))
return -EACCES;
/* If either I or some sibling (!= me) is exclusive, we can't overlap */
list_for_each_entry(cont, &par->css.cgroup->children, sibling) {
c = cgroup_cs(cont);
if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
c != cur &&
cpus_intersects(trial->cpus_allowed, c->cpus_allowed))
return -EINVAL;
if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
c != cur &&
nodes_intersects(trial->mems_allowed, c->mems_allowed))
return -EINVAL;
}
/* Cpusets with tasks can't have empty cpus_allowed or mems_allowed */
if (cgroup_task_count(cur->css.cgroup)) {
if (cpus_empty(trial->cpus_allowed) ||
nodes_empty(trial->mems_allowed)) {
return -ENOSPC;
}
}
return 0;
}
/*
* Helper routine for rebuild_sched_domains().
* Do cpusets a, b have overlapping cpus_allowed masks?
*/
static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
{
return cpus_intersects(a->cpus_allowed, b->cpus_allowed);
}
/*
* rebuild_sched_domains()
*
* If the flag 'sched_load_balance' of any cpuset with non-empty
* 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
* which has that flag enabled, or if any cpuset with a non-empty
* 'cpus' is removed, then call this routine to rebuild the
* scheduler's dynamic sched domains.
*
* This routine builds a partial partition of the systems CPUs
* (the set of non-overlappping cpumask_t's in the array 'part'
* below), and passes that partial partition to the kernel/sched.c
* partition_sched_domains() routine, which will rebuild the
* schedulers load balancing domains (sched domains) as specified
* by that partial partition. A 'partial partition' is a set of
* non-overlapping subsets whose union is a subset of that set.
*
* See "What is sched_load_balance" in Documentation/cpusets.txt
* for a background explanation of this.
*
* Does not return errors, on the theory that the callers of this
* routine would rather not worry about failures to rebuild sched
* domains when operating in the severe memory shortage situations
* that could cause allocation failures below.
*
* Call with cgroup_mutex held. May take callback_mutex during
* call due to the kfifo_alloc() and kmalloc() calls. May nest
* a call to the lock_cpu_hotplug()/unlock_cpu_hotplug() pair.
* Must not be called holding callback_mutex, because we must not
* call lock_cpu_hotplug() while holding callback_mutex. Elsewhere
* the kernel nests callback_mutex inside lock_cpu_hotplug() calls.
* So the reverse nesting would risk an ABBA deadlock.
*
* The three key local variables below are:
* q - a kfifo queue of cpuset pointers, used to implement a
* top-down scan of all cpusets. This scan loads a pointer
* to each cpuset marked is_sched_load_balance into the
* array 'csa'. For our purposes, rebuilding the schedulers
* sched domains, we can ignore !is_sched_load_balance cpusets.
* csa - (for CpuSet Array) Array of pointers to all the cpusets
* that need to be load balanced, for convenient iterative
* access by the subsequent code that finds the best partition,
* i.e the set of domains (subsets) of CPUs such that the
* cpus_allowed of every cpuset marked is_sched_load_balance
* is a subset of one of these domains, while there are as
* many such domains as possible, each as small as possible.
* doms - Conversion of 'csa' to an array of cpumasks, for passing to
* the kernel/sched.c routine partition_sched_domains() in a
* convenient format, that can be easily compared to the prior
* value to determine what partition elements (sched domains)
* were changed (added or removed.)
*
* Finding the best partition (set of domains):
* The triple nested loops below over i, j, k scan over the
* load balanced cpusets (using the array of cpuset pointers in
* csa[]) looking for pairs of cpusets that have overlapping
* cpus_allowed, but which don't have the same 'pn' partition
* number and gives them in the same partition number. It keeps
* looping on the 'restart' label until it can no longer find
* any such pairs.
*
* The union of the cpus_allowed masks from the set of
* all cpusets having the same 'pn' value then form the one
* element of the partition (one sched domain) to be passed to
* partition_sched_domains().
*/
static void rebuild_sched_domains(void)
{
struct kfifo *q; /* queue of cpusets to be scanned */
struct cpuset *cp; /* scans q */
struct cpuset **csa; /* array of all cpuset ptrs */
int csn; /* how many cpuset ptrs in csa so far */
int i, j, k; /* indices for partition finding loops */
cpumask_t *doms; /* resulting partition; i.e. sched domains */
int ndoms; /* number of sched domains in result */
int nslot; /* next empty doms[] cpumask_t slot */
q = NULL;
csa = NULL;
doms = NULL;
/* Special case for the 99% of systems with one, full, sched domain */
if (is_sched_load_balance(&top_cpuset)) {
ndoms = 1;
doms = kmalloc(sizeof(cpumask_t), GFP_KERNEL);
if (!doms)
goto rebuild;
*doms = top_cpuset.cpus_allowed;
goto rebuild;
}
q = kfifo_alloc(number_of_cpusets * sizeof(cp), GFP_KERNEL, NULL);
if (IS_ERR(q))
goto done;
csa = kmalloc(number_of_cpusets * sizeof(cp), GFP_KERNEL);
if (!csa)
goto done;
csn = 0;
cp = &top_cpuset;
__kfifo_put(q, (void *)&cp, sizeof(cp));
while (__kfifo_get(q, (void *)&cp, sizeof(cp))) {
struct cgroup *cont;
struct cpuset *child; /* scans child cpusets of cp */
if (is_sched_load_balance(cp))
csa[csn++] = cp;
list_for_each_entry(cont, &cp->css.cgroup->children, sibling) {
child = cgroup_cs(cont);
__kfifo_put(q, (void *)&child, sizeof(cp));
}
}
for (i = 0; i < csn; i++)
csa[i]->pn = i;
ndoms = csn;
restart:
/* Find the best partition (set of sched domains) */
for (i = 0; i < csn; i++) {
struct cpuset *a = csa[i];
int apn = a->pn;
for (j = 0; j < csn; j++) {
struct cpuset *b = csa[j];
int bpn = b->pn;
if (apn != bpn && cpusets_overlap(a, b)) {
for (k = 0; k < csn; k++) {
struct cpuset *c = csa[k];
if (c->pn == bpn)
c->pn = apn;
}
ndoms--; /* one less element */
goto restart;
}
}
}
/* Convert <csn, csa> to <ndoms, doms> */
doms = kmalloc(ndoms * sizeof(cpumask_t), GFP_KERNEL);
if (!doms)
goto rebuild;
for (nslot = 0, i = 0; i < csn; i++) {
struct cpuset *a = csa[i];
int apn = a->pn;
if (apn >= 0) {
cpumask_t *dp = doms + nslot;
if (nslot == ndoms) {
static int warnings = 10;
if (warnings) {
printk(KERN_WARNING
"rebuild_sched_domains confused:"
" nslot %d, ndoms %d, csn %d, i %d,"
" apn %d\n",
nslot, ndoms, csn, i, apn);
warnings--;
}
continue;
}
cpus_clear(*dp);
for (j = i; j < csn; j++) {
struct cpuset *b = csa[j];
if (apn == b->pn) {
cpus_or(*dp, *dp, b->cpus_allowed);
b->pn = -1;
}
}
nslot++;
}
}
BUG_ON(nslot != ndoms);
rebuild:
/* Have scheduler rebuild sched domains */
lock_cpu_hotplug();
partition_sched_domains(ndoms, doms);
unlock_cpu_hotplug();
done:
if (q && !IS_ERR(q))
kfifo_free(q);
kfree(csa);
/* Don't kfree(doms) -- partition_sched_domains() does that. */
}
static inline int started_after_time(struct task_struct *t1,
struct timespec *time,
struct task_struct *t2)
{
int start_diff = timespec_compare(&t1->start_time, time);
if (start_diff > 0) {
return 1;
} else if (start_diff < 0) {
return 0;
} else {
/*
* Arbitrarily, if two processes started at the same
* time, we'll say that the lower pointer value
* started first. Note that t2 may have exited by now
* so this may not be a valid pointer any longer, but
* that's fine - it still serves to distinguish
* between two tasks started (effectively)
* simultaneously.
*/
return t1 > t2;
}
}
static inline int started_after(void *p1, void *p2)
{
struct task_struct *t1 = p1;
struct task_struct *t2 = p2;
return started_after_time(t1, &t2->start_time, t2);
}
/*
* Call with manage_mutex held. May take callback_mutex during call.
*/
static int update_cpumask(struct cpuset *cs, char *buf)
{
struct cpuset trialcs;
int retval, i;
int is_load_balanced;
struct cgroup_iter it;
struct cgroup *cgrp = cs->css.cgroup;
struct task_struct *p, *dropped;
/* Never dereference latest_task, since it's not refcounted */
struct task_struct *latest_task = NULL;
struct ptr_heap heap;
struct timespec latest_time = { 0, 0 };
/* top_cpuset.cpus_allowed tracks cpu_online_map; it's read-only */
if (cs == &top_cpuset)
return -EACCES;
trialcs = *cs;
/*
* An empty cpus_allowed is ok iff there are no tasks in the cpuset.
* Since cpulist_parse() fails on an empty mask, we special case
* that parsing. The validate_change() call ensures that cpusets
* with tasks have cpus.
*/
buf = strstrip(buf);
if (!*buf) {
cpus_clear(trialcs.cpus_allowed);
} else {
retval = cpulist_parse(buf, trialcs.cpus_allowed);
if (retval < 0)
return retval;
}
cpus_and(trialcs.cpus_allowed, trialcs.cpus_allowed, cpu_online_map);
retval = validate_change(cs, &trialcs);
if (retval < 0)
return retval;
/* Nothing to do if the cpus didn't change */
if (cpus_equal(cs->cpus_allowed, trialcs.cpus_allowed))
return 0;
retval = heap_init(&heap, PAGE_SIZE, GFP_KERNEL, &started_after);
if (retval)
return retval;
is_load_balanced = is_sched_load_balance(&trialcs);
mutex_lock(&callback_mutex);
cs->cpus_allowed = trialcs.cpus_allowed;
mutex_unlock(&callback_mutex);
again:
/*
* Scan tasks in the cpuset, and update the cpumasks of any
* that need an update. Since we can't call set_cpus_allowed()
* while holding tasklist_lock, gather tasks to be processed
* in a heap structure. If the statically-sized heap fills up,
* overflow tasks that started later, and in future iterations
* only consider tasks that started after the latest task in
* the previous pass. This guarantees forward progress and
* that we don't miss any tasks
*/
heap.size = 0;
cgroup_iter_start(cgrp, &it);
while ((p = cgroup_iter_next(cgrp, &it))) {
/* Only affect tasks that don't have the right cpus_allowed */
if (cpus_equal(p->cpus_allowed, cs->cpus_allowed))
continue;
/*
* Only process tasks that started after the last task
* we processed
*/
if (!started_after_time(p, &latest_time, latest_task))
continue;
dropped = heap_insert(&heap, p);
if (dropped == NULL) {
get_task_struct(p);
} else if (dropped != p) {
get_task_struct(p);
put_task_struct(dropped);
}
}
cgroup_iter_end(cgrp, &it);
if (heap.size) {
for (i = 0; i < heap.size; i++) {
struct task_struct *p = heap.ptrs[i];
if (i == 0) {
latest_time = p->start_time;
latest_task = p;
}
set_cpus_allowed(p, cs->cpus_allowed);
put_task_struct(p);
}
/*
* If we had to process any tasks at all, scan again
* in case some of them were in the middle of forking
* children that didn't notice the new cpumask
* restriction. Not the most efficient way to do it,
* but it avoids having to take callback_mutex in the
* fork path
*/
goto again;
}
heap_free(&heap);
if (is_load_balanced)
rebuild_sched_domains();
return 0;
}
/*
* cpuset_migrate_mm
*
* Migrate memory region from one set of nodes to another.
*
* Temporarilly set tasks mems_allowed to target nodes of migration,
* so that the migration code can allocate pages on these nodes.
*
* Call holding manage_mutex, so our current->cpuset won't change
* during this call, as manage_mutex holds off any attach_task()
* calls. Therefore we don't need to take task_lock around the
* call to guarantee_online_mems(), as we know no one is changing
* our tasks cpuset.
*
* Hold callback_mutex around the two modifications of our tasks
* mems_allowed to synchronize with cpuset_mems_allowed().
*
* While the mm_struct we are migrating is typically from some
* other task, the task_struct mems_allowed that we are hacking
* is for our current task, which must allocate new pages for that
* migrating memory region.
*
* We call cpuset_update_task_memory_state() before hacking
* our tasks mems_allowed, so that we are assured of being in
* sync with our tasks cpuset, and in particular, callbacks to
* cpuset_update_task_memory_state() from nested page allocations
* won't see any mismatch of our cpuset and task mems_generation
* values, so won't overwrite our hacked tasks mems_allowed
* nodemask.
*/
static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
const nodemask_t *to)
{
struct task_struct *tsk = current;
cpuset_update_task_memory_state();
mutex_lock(&callback_mutex);
tsk->mems_allowed = *to;
mutex_unlock(&callback_mutex);
do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);
mutex_lock(&callback_mutex);
guarantee_online_mems(task_cs(tsk),&tsk->mems_allowed);
mutex_unlock(&callback_mutex);
}
/*
* Handle user request to change the 'mems' memory placement
* of a cpuset. Needs to validate the request, update the
* cpusets mems_allowed and mems_generation, and for each
* task in the cpuset, rebind any vma mempolicies and if
* the cpuset is marked 'memory_migrate', migrate the tasks
* pages to the new memory.
*
* Call with manage_mutex held. May take callback_mutex during call.
* Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
* lock each such tasks mm->mmap_sem, scan its vma's and rebind
* their mempolicies to the cpusets new mems_allowed.
*/
static void *cpuset_being_rebound;
static int update_nodemask(struct cpuset *cs, char *buf)
{
struct cpuset trialcs;
nodemask_t oldmem;
struct task_struct *p;
struct mm_struct **mmarray;
int i, n, ntasks;
int migrate;
int fudge;
int retval;
struct cgroup_iter it;
/*
* top_cpuset.mems_allowed tracks node_stats[N_HIGH_MEMORY];
* it's read-only
*/
if (cs == &top_cpuset)
return -EACCES;
trialcs = *cs;
/*
* An empty mems_allowed is ok iff there are no tasks in the cpuset.
* Since nodelist_parse() fails on an empty mask, we special case
* that parsing. The validate_change() call ensures that cpusets
* with tasks have memory.
*/
buf = strstrip(buf);
if (!*buf) {
nodes_clear(trialcs.mems_allowed);
} else {
retval = nodelist_parse(buf, trialcs.mems_allowed);
if (retval < 0)
goto done;
}
nodes_and(trialcs.mems_allowed, trialcs.mems_allowed,
node_states[N_HIGH_MEMORY]);
oldmem = cs->mems_allowed;
if (nodes_equal(oldmem, trialcs.mems_allowed)) {
retval = 0; /* Too easy - nothing to do */
goto done;
}
retval = validate_change(cs, &trialcs);
if (retval < 0)
goto done;
mutex_lock(&callback_mutex);
cs->mems_allowed = trialcs.mems_allowed;
cs->mems_generation = cpuset_mems_generation++;
mutex_unlock(&callback_mutex);
cpuset_being_rebound = cs; /* causes mpol_copy() rebind */
fudge = 10; /* spare mmarray[] slots */
fudge += cpus_weight(cs->cpus_allowed); /* imagine one fork-bomb/cpu */
retval = -ENOMEM;
/*
* Allocate mmarray[] to hold mm reference for each task
* in cpuset cs. Can't kmalloc GFP_KERNEL while holding
* tasklist_lock. We could use GFP_ATOMIC, but with a
* few more lines of code, we can retry until we get a big
* enough mmarray[] w/o using GFP_ATOMIC.
*/
while (1) {
ntasks = cgroup_task_count(cs->css.cgroup); /* guess */
ntasks += fudge;
mmarray = kmalloc(ntasks * sizeof(*mmarray), GFP_KERNEL);
if (!mmarray)
goto done;
read_lock(&tasklist_lock); /* block fork */
if (cgroup_task_count(cs->css.cgroup) <= ntasks)
break; /* got enough */
read_unlock(&tasklist_lock); /* try again */
kfree(mmarray);
}
n = 0;
/* Load up mmarray[] with mm reference for each task in cpuset. */
cgroup_iter_start(cs->css.cgroup, &it);
while ((p = cgroup_iter_next(cs->css.cgroup, &it))) {
struct mm_struct *mm;
if (n >= ntasks) {
printk(KERN_WARNING
"Cpuset mempolicy rebind incomplete.\n");
break;
}
mm = get_task_mm(p);
if (!mm)
continue;
mmarray[n++] = mm;
}
cgroup_iter_end(cs->css.cgroup, &it);
read_unlock(&tasklist_lock);
/*
* Now that we've dropped the tasklist spinlock, we can
* rebind the vma mempolicies of each mm in mmarray[] to their
* new cpuset, and release that mm. The mpol_rebind_mm()
* call takes mmap_sem, which we couldn't take while holding
* tasklist_lock. Forks can happen again now - the mpol_copy()
* cpuset_being_rebound check will catch such forks, and rebind
* their vma mempolicies too. Because we still hold the global
* cpuset manage_mutex, we know that no other rebind effort will
* be contending for the global variable cpuset_being_rebound.
* It's ok if we rebind the same mm twice; mpol_rebind_mm()
* is idempotent. Also migrate pages in each mm to new nodes.
*/
migrate = is_memory_migrate(cs);
for (i = 0; i < n; i++) {
struct mm_struct *mm = mmarray[i];
mpol_rebind_mm(mm, &cs->mems_allowed);
if (migrate)
cpuset_migrate_mm(mm, &oldmem, &cs->mems_allowed);
mmput(mm);
}
/* We're done rebinding vma's to this cpusets new mems_allowed. */
kfree(mmarray);
cpuset_being_rebound = NULL;
retval = 0;
done:
return retval;
}
int current_cpuset_is_being_rebound(void)
{
return task_cs(current) == cpuset_being_rebound;
}
/*
* Call with manage_mutex held.
*/
static int update_memory_pressure_enabled(struct cpuset *cs, char *buf)
{
if (simple_strtoul(buf, NULL, 10) != 0)
cpuset_memory_pressure_enabled = 1;
else
cpuset_memory_pressure_enabled = 0;
return 0;
}
/*
* update_flag - read a 0 or a 1 in a file and update associated flag
* bit: the bit to update (CS_CPU_EXCLUSIVE, CS_MEM_EXCLUSIVE,
* CS_SCHED_LOAD_BALANCE,
* CS_NOTIFY_ON_RELEASE, CS_MEMORY_MIGRATE,
* CS_SPREAD_PAGE, CS_SPREAD_SLAB)
* cs: the cpuset to update
* buf: the buffer where we read the 0 or 1
*
* Call with manage_mutex held.
*/
static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf)
{
int turning_on;
struct cpuset trialcs;
int err;
int cpus_nonempty, balance_flag_changed;
turning_on = (simple_strtoul(buf, NULL, 10) != 0);
trialcs = *cs;
if (turning_on)
set_bit(bit, &trialcs.flags);
else
clear_bit(bit, &trialcs.flags);
err = validate_change(cs, &trialcs);
if (err < 0)
return err;
cpus_nonempty = !cpus_empty(trialcs.cpus_allowed);
balance_flag_changed = (is_sched_load_balance(cs) !=
is_sched_load_balance(&trialcs));
mutex_lock(&callback_mutex);
cs->flags = trialcs.flags;
mutex_unlock(&callback_mutex);
if (cpus_nonempty && balance_flag_changed)
rebuild_sched_domains();
return 0;
}
/*
* Frequency meter - How fast is some event occurring?
*
* These routines manage a digitally filtered, constant time based,
* event frequency meter. There are four routines:
* fmeter_init() - initialize a frequency meter.
* fmeter_markevent() - called each time the event happens.
* fmeter_getrate() - returns the recent rate of such events.
* fmeter_update() - internal routine used to update fmeter.
*
* A common data structure is passed to each of these routines,
* which is used to keep track of the state required to manage the
* frequency meter and its digital filter.
*
* The filter works on the number of events marked per unit time.
* The filter is single-pole low-pass recursive (IIR). The time unit
* is 1 second. Arithmetic is done using 32-bit integers scaled to
* simulate 3 decimal digits of precision (multiplied by 1000).
*
* With an FM_COEF of 933, and a time base of 1 second, the filter
* has a half-life of 10 seconds, meaning that if the events quit
* happening, then the rate returned from the fmeter_getrate()
* will be cut in half each 10 seconds, until it converges to zero.
*
* It is not worth doing a real infinitely recursive filter. If more
* than FM_MAXTICKS ticks have elapsed since the last filter event,
* just compute FM_MAXTICKS ticks worth, by which point the level
* will be stable.
*
* Limit the count of unprocessed events to FM_MAXCNT, so as to avoid
* arithmetic overflow in the fmeter_update() routine.
*
* Given the simple 32 bit integer arithmetic used, this meter works
* best for reporting rates between one per millisecond (msec) and
* one per 32 (approx) seconds. At constant rates faster than one
* per msec it maxes out at values just under 1,000,000. At constant
* rates between one per msec, and one per second it will stabilize
* to a value N*1000, where N is the rate of events per second.
* At constant rates between one per second and one per 32 seconds,
* it will be choppy, moving up on the seconds that have an event,
* and then decaying until the next event. At rates slower than
* about one in 32 seconds, it decays all the way back to zero between
* each event.
*/
#define FM_COEF 933 /* coefficient for half-life of 10 secs */
#define FM_MAXTICKS ((time_t)99) /* useless computing more ticks than this */
#define FM_MAXCNT 1000000 /* limit cnt to avoid overflow */
#define FM_SCALE 1000 /* faux fixed point scale */
/* Initialize a frequency meter */
static void fmeter_init(struct fmeter *fmp)
{
fmp->cnt = 0;
fmp->val = 0;
fmp->time = 0;
spin_lock_init(&fmp->lock);
}
/* Internal meter update - process cnt events and update value */
static void fmeter_update(struct fmeter *fmp)
{
time_t now = get_seconds();
time_t ticks = now - fmp->time;
if (ticks == 0)
return;
ticks = min(FM_MAXTICKS, ticks);
while (ticks-- > 0)
fmp->val = (FM_COEF * fmp->val) / FM_SCALE;
fmp->time = now;
fmp->val += ((FM_SCALE - FM_COEF) * fmp->cnt) / FM_SCALE;
fmp->cnt = 0;
}
/* Process any previous ticks, then bump cnt by one (times scale). */
static void fmeter_markevent(struct fmeter *fmp)
{
spin_lock(&fmp->lock);
fmeter_update(fmp);
fmp->cnt = min(FM_MAXCNT, fmp->cnt + FM_SCALE);
spin_unlock(&fmp->lock);
}
/* Process any previous ticks, then return current value. */
static int fmeter_getrate(struct fmeter *fmp)
{
int val;
spin_lock(&fmp->lock);
fmeter_update(fmp);
val = fmp->val;
spin_unlock(&fmp->lock);
return val;
}
static int cpuset_can_attach(struct cgroup_subsys *ss,
struct cgroup *cont, struct task_struct *tsk)
{
struct cpuset *cs = cgroup_cs(cont);
if (cpus_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
return -ENOSPC;
return security_task_setscheduler(tsk, 0, NULL);
}
static void cpuset_attach(struct cgroup_subsys *ss,
struct cgroup *cont, struct cgroup *oldcont,
struct task_struct *tsk)
{
cpumask_t cpus;
nodemask_t from, to;
struct mm_struct *mm;
struct cpuset *cs = cgroup_cs(cont);
struct cpuset *oldcs = cgroup_cs(oldcont);
mutex_lock(&callback_mutex);
guarantee_online_cpus(cs, &cpus);
set_cpus_allowed(tsk, cpus);
mutex_unlock(&callback_mutex);
from = oldcs->mems_allowed;
to = cs->mems_allowed;
mm = get_task_mm(tsk);
if (mm) {
mpol_rebind_mm(mm, &to);
if (is_memory_migrate(cs))
cpuset_migrate_mm(mm, &from, &to);
mmput(mm);
}
}
/* The various types of files and directories in a cpuset file system */
typedef enum {
FILE_MEMORY_MIGRATE,
FILE_CPULIST,
FILE_MEMLIST,
FILE_CPU_EXCLUSIVE,
FILE_MEM_EXCLUSIVE,
FILE_SCHED_LOAD_BALANCE,
FILE_MEMORY_PRESSURE_ENABLED,
FILE_MEMORY_PRESSURE,
FILE_SPREAD_PAGE,
FILE_SPREAD_SLAB,
} cpuset_filetype_t;
static ssize_t cpuset_common_file_write(struct cgroup *cont,
struct cftype *cft,
struct file *file,
const char __user *userbuf,
size_t nbytes, loff_t *unused_ppos)
{
struct cpuset *cs = cgroup_cs(cont);
cpuset_filetype_t type = cft->private;
char *buffer;
int retval = 0;
/* Crude upper limit on largest legitimate cpulist user might write. */
if (nbytes > 100U + 6 * max(NR_CPUS, MAX_NUMNODES))
return -E2BIG;
/* +1 for nul-terminator */
if ((buffer = kmalloc(nbytes + 1, GFP_KERNEL)) == 0)
return -ENOMEM;
if (copy_from_user(buffer, userbuf, nbytes)) {
retval = -EFAULT;
goto out1;
}
buffer[nbytes] = 0; /* nul-terminate */
cgroup_lock();
if (cgroup_is_removed(cont)) {
retval = -ENODEV;
goto out2;
}
switch (type) {
case FILE_CPULIST:
retval = update_cpumask(cs, buffer);
break;
case FILE_MEMLIST:
retval = update_nodemask(cs, buffer);
break;
case FILE_CPU_EXCLUSIVE:
retval = update_flag(CS_CPU_EXCLUSIVE, cs, buffer);
break;
case FILE_MEM_EXCLUSIVE:
retval = update_flag(CS_MEM_EXCLUSIVE, cs, buffer);
break;
case FILE_SCHED_LOAD_BALANCE:
retval = update_flag(CS_SCHED_LOAD_BALANCE, cs, buffer);
break;
case FILE_MEMORY_MIGRATE:
retval = update_flag(CS_MEMORY_MIGRATE, cs, buffer);
break;
case FILE_MEMORY_PRESSURE_ENABLED:
retval = update_memory_pressure_enabled(cs, buffer);
break;
case FILE_MEMORY_PRESSURE:
retval = -EACCES;
break;
case FILE_SPREAD_PAGE:
retval = update_flag(CS_SPREAD_PAGE, cs, buffer);
cs->mems_generation = cpuset_mems_generation++;
break;
case FILE_SPREAD_SLAB:
retval = update_flag(CS_SPREAD_SLAB, cs, buffer);
cs->mems_generation = cpuset_mems_generation++;
break;
default:
retval = -EINVAL;
goto out2;
}
if (retval == 0)
retval = nbytes;
out2:
cgroup_unlock();
out1:
kfree(buffer);
return retval;
}
/*
* These ascii lists should be read in a single call, by using a user
* buffer large enough to hold the entire map. If read in smaller
* chunks, there is no guarantee of atomicity. Since the display format
* used, list of ranges of sequential numbers, is variable length,
* and since these maps can change value dynamically, one could read
* gibberish by doing partial reads while a list was changing.
* A single large read to a buffer that crosses a page boundary is
* ok, because the result being copied to user land is not recomputed
* across a page fault.
*/
static int cpuset_sprintf_cpulist(char *page, struct cpuset *cs)
{
cpumask_t mask;
mutex_lock(&callback_mutex);
mask = cs->cpus_allowed;
mutex_unlock(&callback_mutex);
return cpulist_scnprintf(page, PAGE_SIZE, mask);
}
static int cpuset_sprintf_memlist(char *page, struct cpuset *cs)
{
nodemask_t mask;
mutex_lock(&callback_mutex);
mask = cs->mems_allowed;
mutex_unlock(&callback_mutex);
return nodelist_scnprintf(page, PAGE_SIZE, mask);
}
static ssize_t cpuset_common_file_read(struct cgroup *cont,
struct cftype *cft,
struct file *file,
char __user *buf,
size_t nbytes, loff_t *ppos)
{
struct cpuset *cs = cgroup_cs(cont);
cpuset_filetype_t type = cft->private;
char *page;
ssize_t retval = 0;
char *s;
if (!(page = (char *)__get_free_page(GFP_TEMPORARY)))
return -ENOMEM;
s = page;
switch (type) {
case FILE_CPULIST:
s += cpuset_sprintf_cpulist(s, cs);
break;
case FILE_MEMLIST:
s += cpuset_sprintf_memlist(s, cs);
break;
case FILE_CPU_EXCLUSIVE:
*s++ = is_cpu_exclusive(cs) ? '1' : '0';
break;
case FILE_MEM_EXCLUSIVE:
*s++ = is_mem_exclusive(cs) ? '1' : '0';
break;
case FILE_SCHED_LOAD_BALANCE:
*s++ = is_sched_load_balance(cs) ? '1' : '0';
break;
case FILE_MEMORY_MIGRATE:
*s++ = is_memory_migrate(cs) ? '1' : '0';
break;
case FILE_MEMORY_PRESSURE_ENABLED:
*s++ = cpuset_memory_pressure_enabled ? '1' : '0';
break;
case FILE_MEMORY_PRESSURE:
s += sprintf(s, "%d", fmeter_getrate(&cs->fmeter));
break;
case FILE_SPREAD_PAGE:
*s++ = is_spread_page(cs) ? '1' : '0';
break;
case FILE_SPREAD_SLAB:
*s++ = is_spread_slab(cs) ? '1' : '0';
break;
default:
retval = -EINVAL;
goto out;
}
*s++ = '\n';
retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page);
out:
free_page((unsigned long)page);
return retval;
}
/*
* for the common functions, 'private' gives the type of file
*/
static struct cftype cft_cpus = {
.name = "cpus",
.read = cpuset_common_file_read,
.write = cpuset_common_file_write,
.private = FILE_CPULIST,
};
static struct cftype cft_mems = {
.name = "mems",
.read = cpuset_common_file_read,
.write = cpuset_common_file_write,
.private = FILE_MEMLIST,
};
static struct cftype cft_cpu_exclusive = {
.name = "cpu_exclusive",
.read = cpuset_common_file_read,
.write = cpuset_common_file_write,
.private = FILE_CPU_EXCLUSIVE,
};
static struct cftype cft_mem_exclusive = {
.name = "mem_exclusive",
.read = cpuset_common_file_read,
.write = cpuset_common_file_write,
.private = FILE_MEM_EXCLUSIVE,
};
static struct cftype cft_sched_load_balance = {
.name = "sched_load_balance",
.read = cpuset_common_file_read,
.write = cpuset_common_file_write,
.private = FILE_SCHED_LOAD_BALANCE,
};
static struct cftype cft_memory_migrate = {
.name = "memory_migrate",
.read = cpuset_common_file_read,
.write = cpuset_common_file_write,
.private = FILE_MEMORY_MIGRATE,
};
static struct cftype cft_memory_pressure_enabled = {
.name = "memory_pressure_enabled",
.read = cpuset_common_file_read,
.write = cpuset_common_file_write,
.private = FILE_MEMORY_PRESSURE_ENABLED,
};
static struct cftype cft_memory_pressure = {
.name = "memory_pressure",
.read = cpuset_common_file_read,
.write = cpuset_common_file_write,
.private = FILE_MEMORY_PRESSURE,
};
static struct cftype cft_spread_page = {
.name = "memory_spread_page",
.read = cpuset_common_file_read,
.write = cpuset_common_file_write,
.private = FILE_SPREAD_PAGE,
};
static struct cftype cft_spread_slab = {
.name = "memory_spread_slab",
.read = cpuset_common_file_read,
.write = cpuset_common_file_write,
.private = FILE_SPREAD_SLAB,
};
static int cpuset_populate(struct cgroup_subsys *ss, struct cgroup *cont)
{
int err;
if ((err = cgroup_add_file(cont, ss, &cft_cpus)) < 0)
return err;
if ((err = cgroup_add_file(cont, ss, &cft_mems)) < 0)
return err;
if ((err = cgroup_add_file(cont, ss, &cft_cpu_exclusive)) < 0)
return err;
if ((err = cgroup_add_file(cont, ss, &cft_mem_exclusive)) < 0)
return err;
if ((err = cgroup_add_file(cont, ss, &cft_memory_migrate)) < 0)
return err;
if ((err = cgroup_add_file(cont, ss, &cft_sched_load_balance)) < 0)
return err;
if ((err = cgroup_add_file(cont, ss, &cft_memory_pressure)) < 0)
return err;
if ((err = cgroup_add_file(cont, ss, &cft_spread_page)) < 0)
return err;
if ((err = cgroup_add_file(cont, ss, &cft_spread_slab)) < 0)
return err;
/* memory_pressure_enabled is in root cpuset only */
if (err == 0 && !cont->parent)
err = cgroup_add_file(cont, ss,
&cft_memory_pressure_enabled);
return 0;
}
/*
* post_clone() is called at the end of cgroup_clone().
* 'cgroup' was just created automatically as a result of
* a cgroup_clone(), and the current task is about to
* be moved into 'cgroup'.
*
* Currently we refuse to set up the cgroup - thereby
* refusing the task to be entered, and as a result refusing
* the sys_unshare() or clone() which initiated it - if any
* sibling cpusets have exclusive cpus or mem.
*
* If this becomes a problem for some users who wish to
* allow that scenario, then cpuset_post_clone() could be
* changed to grant parent->cpus_allowed-sibling_cpus_exclusive
* (and likewise for mems) to the new cgroup.
*/
static void cpuset_post_clone(struct cgroup_subsys *ss,
struct cgroup *cgroup)
{
struct cgroup *parent, *child;
struct cpuset *cs, *parent_cs;
parent = cgroup->parent;
list_for_each_entry(child, &parent->children, sibling) {
cs = cgroup_cs(child);
if (is_mem_exclusive(cs) || is_cpu_exclusive(cs))
return;
}
cs = cgroup_cs(cgroup);
parent_cs = cgroup_cs(parent);
cs->mems_allowed = parent_cs->mems_allowed;
cs->cpus_allowed = parent_cs->cpus_allowed;
return;
}
/*
* cpuset_create - create a cpuset
* parent: cpuset that will be parent of the new cpuset.
* name: name of the new cpuset. Will be strcpy'ed.
* mode: mode to set on new inode
*
* Must be called with the mutex on the parent inode held
*/
static struct cgroup_subsys_state *cpuset_create(
struct cgroup_subsys *ss,
struct cgroup *cont)
{
struct cpuset *cs;
struct cpuset *parent;
if (!cont->parent) {
/* This is early initialization for the top cgroup */
top_cpuset.mems_generation = cpuset_mems_generation++;
return &top_cpuset.css;
}
parent = cgroup_cs(cont->parent);
cs = kmalloc(sizeof(*cs), GFP_KERNEL);
if (!cs)
return ERR_PTR(-ENOMEM);
cpuset_update_task_memory_state();
cs->flags = 0;
if (is_spread_page(parent))
set_bit(CS_SPREAD_PAGE, &cs->flags);
if (is_spread_slab(parent))
set_bit(CS_SPREAD_SLAB, &cs->flags);
set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
cs->cpus_allowed = CPU_MASK_NONE;
cs->mems_allowed = NODE_MASK_NONE;
cs->mems_generation = cpuset_mems_generation++;
fmeter_init(&cs->fmeter);
cs->parent = parent;
number_of_cpusets++;
return &cs->css ;
}
/*
* Locking note on the strange update_flag() call below:
*
* If the cpuset being removed has its flag 'sched_load_balance'
* enabled, then simulate turning sched_load_balance off, which
* will call rebuild_sched_domains(). The lock_cpu_hotplug()
* call in rebuild_sched_domains() must not be made while holding
* callback_mutex. Elsewhere the kernel nests callback_mutex inside
* lock_cpu_hotplug() calls. So the reverse nesting would risk an
* ABBA deadlock.
*/
static void cpuset_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
{
struct cpuset *cs = cgroup_cs(cont);
cpuset_update_task_memory_state();
if (is_sched_load_balance(cs))
update_flag(CS_SCHED_LOAD_BALANCE, cs, "0");
number_of_cpusets--;
kfree(cs);
}
struct cgroup_subsys cpuset_subsys = {
.name = "cpuset",
.create = cpuset_create,
.destroy = cpuset_destroy,
.can_attach = cpuset_can_attach,
.attach = cpuset_attach,
.populate = cpuset_populate,
.post_clone = cpuset_post_clone,
.subsys_id = cpuset_subsys_id,
.early_init = 1,
};
/*
* cpuset_init_early - just enough so that the calls to
* cpuset_update_task_memory_state() in early init code
* are harmless.
*/
int __init cpuset_init_early(void)
{
top_cpuset.mems_generation = cpuset_mems_generation++;
return 0;
}
/**
* cpuset_init - initialize cpusets at system boot
*
* Description: Initialize top_cpuset and the cpuset internal file system,
**/
int __init cpuset_init(void)
{
int err = 0;
top_cpuset.cpus_allowed = CPU_MASK_ALL;
top_cpuset.mems_allowed = NODE_MASK_ALL;
fmeter_init(&top_cpuset.fmeter);
top_cpuset.mems_generation = cpuset_mems_generation++;
set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags);
err = register_filesystem(&cpuset_fs_type);
if (err < 0)
return err;
number_of_cpusets = 1;
return 0;
}
/*
* If common_cpu_mem_hotplug_unplug(), below, unplugs any CPUs
* or memory nodes, we need to walk over the cpuset hierarchy,
* removing that CPU or node from all cpusets. If this removes the
* last CPU or node from a cpuset, then the guarantee_online_cpus()
* or guarantee_online_mems() code will use that emptied cpusets
* parent online CPUs or nodes. Cpusets that were already empty of
* CPUs or nodes are left empty.
*
* This routine is intentionally inefficient in a couple of regards.
* It will check all cpusets in a subtree even if the top cpuset of
* the subtree has no offline CPUs or nodes. It checks both CPUs and
* nodes, even though the caller could have been coded to know that
* only one of CPUs or nodes needed to be checked on a given call.
* This was done to minimize text size rather than cpu cycles.
*
* Call with both manage_mutex and callback_mutex held.
*
* Recursive, on depth of cpuset subtree.
*/
static void guarantee_online_cpus_mems_in_subtree(const struct cpuset *cur)
{
struct cgroup *cont;
struct cpuset *c;
/* Each of our child cpusets mems must be online */
list_for_each_entry(cont, &cur->css.cgroup->children, sibling) {
c = cgroup_cs(cont);
guarantee_online_cpus_mems_in_subtree(c);
if (!cpus_empty(c->cpus_allowed))
guarantee_online_cpus(c, &c->cpus_allowed);
if (!nodes_empty(c->mems_allowed))
guarantee_online_mems(c, &c->mems_allowed);
}
}
/*
* The cpus_allowed and mems_allowed nodemasks in the top_cpuset track
* cpu_online_map and node_states[N_HIGH_MEMORY]. Force the top cpuset to
* track what's online after any CPU or memory node hotplug or unplug
* event.
*
* To ensure that we don't remove a CPU or node from the top cpuset
* that is currently in use by a child cpuset (which would violate
* the rule that cpusets must be subsets of their parent), we first
* call the recursive routine guarantee_online_cpus_mems_in_subtree().
*
* Since there are two callers of this routine, one for CPU hotplug
* events and one for memory node hotplug events, we could have coded
* two separate routines here. We code it as a single common routine
* in order to minimize text size.
*/
static void common_cpu_mem_hotplug_unplug(void)
{
cgroup_lock();
mutex_lock(&callback_mutex);
guarantee_online_cpus_mems_in_subtree(&top_cpuset);
top_cpuset.cpus_allowed = cpu_online_map;
top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
mutex_unlock(&callback_mutex);
cgroup_unlock();
}
/*
* The top_cpuset tracks what CPUs and Memory Nodes are online,
* period. This is necessary in order to make cpusets transparent
* (of no affect) on systems that are actively using CPU hotplug
* but making no active use of cpusets.
*
* This routine ensures that top_cpuset.cpus_allowed tracks
* cpu_online_map on each CPU hotplug (cpuhp) event.
*/
static int cpuset_handle_cpuhp(struct notifier_block *unused_nb,
unsigned long phase, void *unused_cpu)
{
if (phase == CPU_DYING || phase == CPU_DYING_FROZEN)
return NOTIFY_DONE;
common_cpu_mem_hotplug_unplug();
return 0;
}
#ifdef CONFIG_MEMORY_HOTPLUG
/*
* Keep top_cpuset.mems_allowed tracking node_states[N_HIGH_MEMORY].
* Call this routine anytime after you change
* node_states[N_HIGH_MEMORY].
* See also the previous routine cpuset_handle_cpuhp().
*/
void cpuset_track_online_nodes(void)
{
common_cpu_mem_hotplug_unplug();
}
#endif
/**
* cpuset_init_smp - initialize cpus_allowed
*
* Description: Finish top cpuset after cpu, node maps are initialized
**/
void __init cpuset_init_smp(void)
{
top_cpuset.cpus_allowed = cpu_online_map;
top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
hotcpu_notifier(cpuset_handle_cpuhp, 0);
}
/**
* cpuset_cpus_allowed - return cpus_allowed mask from a tasks cpuset.
* @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed.
*
* Description: Returns the cpumask_t cpus_allowed of the cpuset
* attached to the specified @tsk. Guaranteed to return some non-empty
* subset of cpu_online_map, even if this means going outside the
* tasks cpuset.
**/
cpumask_t cpuset_cpus_allowed(struct task_struct *tsk)
{
cpumask_t mask;
mutex_lock(&callback_mutex);
mask = cpuset_cpus_allowed_locked(tsk);
mutex_unlock(&callback_mutex);
return mask;
}
/**
* cpuset_cpus_allowed_locked - return cpus_allowed mask from a tasks cpuset.
* Must be called with callback_mutex held.
**/
cpumask_t cpuset_cpus_allowed_locked(struct task_struct *tsk)
{
cpumask_t mask;
task_lock(tsk);
guarantee_online_cpus(task_cs(tsk), &mask);
task_unlock(tsk);
return mask;
}
void cpuset_init_current_mems_allowed(void)
{
current->mems_allowed = NODE_MASK_ALL;
}
/**
* cpuset_mems_allowed - return mems_allowed mask from a tasks cpuset.
* @tsk: pointer to task_struct from which to obtain cpuset->mems_allowed.
*
* Description: Returns the nodemask_t mems_allowed of the cpuset
* attached to the specified @tsk. Guaranteed to return some non-empty
* subset of node_states[N_HIGH_MEMORY], even if this means going outside the
* tasks cpuset.
**/
nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
{
nodemask_t mask;
mutex_lock(&callback_mutex);
task_lock(tsk);
guarantee_online_mems(task_cs(tsk), &mask);
task_unlock(tsk);
mutex_unlock(&callback_mutex);
return mask;
}
/**
* cpuset_zonelist_valid_mems_allowed - check zonelist vs. curremt mems_allowed
* @zl: the zonelist to be checked
*
* Are any of the nodes on zonelist zl allowed in current->mems_allowed?
*/
int cpuset_zonelist_valid_mems_allowed(struct zonelist *zl)
{
int i;
for (i = 0; zl->zones[i]; i++) {
int nid = zone_to_nid(zl->zones[i]);
if (node_isset(nid, current->mems_allowed))
return 1;
}
return 0;
}
/*
* nearest_exclusive_ancestor() - Returns the nearest mem_exclusive
* ancestor to the specified cpuset. Call holding callback_mutex.
* If no ancestor is mem_exclusive (an unusual configuration), then
* returns the root cpuset.
*/
static const struct cpuset *nearest_exclusive_ancestor(const struct cpuset *cs)
{
while (!is_mem_exclusive(cs) && cs->parent)
cs = cs->parent;
return cs;
}
/**
* cpuset_zone_allowed_softwall - Can we allocate on zone z's memory node?
* @z: is this zone on an allowed node?
* @gfp_mask: memory allocation flags
*
* If we're in interrupt, yes, we can always allocate. If
* __GFP_THISNODE is set, yes, we can always allocate. If zone
* z's node is in our tasks mems_allowed, yes. If it's not a
* __GFP_HARDWALL request and this zone's nodes is in the nearest
* mem_exclusive cpuset ancestor to this tasks cpuset, yes.
* If the task has been OOM killed and has access to memory reserves
* as specified by the TIF_MEMDIE flag, yes.
* Otherwise, no.
*
* If __GFP_HARDWALL is set, cpuset_zone_allowed_softwall()
* reduces to cpuset_zone_allowed_hardwall(). Otherwise,
* cpuset_zone_allowed_softwall() might sleep, and might allow a zone
* from an enclosing cpuset.
*
* cpuset_zone_allowed_hardwall() only handles the simpler case of
* hardwall cpusets, and never sleeps.
*
* The __GFP_THISNODE placement logic is really handled elsewhere,
* by forcibly using a zonelist starting at a specified node, and by
* (in get_page_from_freelist()) refusing to consider the zones for
* any node on the zonelist except the first. By the time any such
* calls get to this routine, we should just shut up and say 'yes'.
*
* GFP_USER allocations are marked with the __GFP_HARDWALL bit,
* and do not allow allocations outside the current tasks cpuset
* unless the task has been OOM killed as is marked TIF_MEMDIE.
* GFP_KERNEL allocations are not so marked, so can escape to the
* nearest enclosing mem_exclusive ancestor cpuset.
*
* Scanning up parent cpusets requires callback_mutex. The
* __alloc_pages() routine only calls here with __GFP_HARDWALL bit
* _not_ set if it's a GFP_KERNEL allocation, and all nodes in the
* current tasks mems_allowed came up empty on the first pass over
* the zonelist. So only GFP_KERNEL allocations, if all nodes in the
* cpuset are short of memory, might require taking the callback_mutex
* mutex.
*
* The first call here from mm/page_alloc:get_page_from_freelist()
* has __GFP_HARDWALL set in gfp_mask, enforcing hardwall cpusets,
* so no allocation on a node outside the cpuset is allowed (unless
* in interrupt, of course).
*
* The second pass through get_page_from_freelist() doesn't even call
* here for GFP_ATOMIC calls. For those calls, the __alloc_pages()
* variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
* in alloc_flags. That logic and the checks below have the combined
* affect that:
* in_interrupt - any node ok (current task context irrelevant)
* GFP_ATOMIC - any node ok
* TIF_MEMDIE - any node ok
* GFP_KERNEL - any node in enclosing mem_exclusive cpuset ok
* GFP_USER - only nodes in current tasks mems allowed ok.
*
* Rule:
* Don't call cpuset_zone_allowed_softwall if you can't sleep, unless you
* pass in the __GFP_HARDWALL flag set in gfp_flag, which disables
* the code that might scan up ancestor cpusets and sleep.
*/
int __cpuset_zone_allowed_softwall(struct zone *z, gfp_t gfp_mask)
{
int node; /* node that zone z is on */
const struct cpuset *cs; /* current cpuset ancestors */
int allowed; /* is allocation in zone z allowed? */
if (in_interrupt() || (gfp_mask & __GFP_THISNODE))
return 1;
node = zone_to_nid(z);
might_sleep_if(!(gfp_mask & __GFP_HARDWALL));
if (node_isset(node, current->mems_allowed))
return 1;
/*
* Allow tasks that have access to memory reserves because they have
* been OOM killed to get memory anywhere.
*/
if (unlikely(test_thread_flag(TIF_MEMDIE)))
return 1;
if (gfp_mask & __GFP_HARDWALL) /* If hardwall request, stop here */
return 0;
if (current->flags & PF_EXITING) /* Let dying task have memory */
return 1;
/* Not hardwall and node outside mems_allowed: scan up cpusets */
mutex_lock(&callback_mutex);
task_lock(current);
cs = nearest_exclusive_ancestor(task_cs(current));
task_unlock(current);
allowed = node_isset(node, cs->mems_allowed);
mutex_unlock(&callback_mutex);
return allowed;
}
/*
* cpuset_zone_allowed_hardwall - Can we allocate on zone z's memory node?
* @z: is this zone on an allowed node?
* @gfp_mask: memory allocation flags
*
* If we're in interrupt, yes, we can always allocate.
* If __GFP_THISNODE is set, yes, we can always allocate. If zone
* z's node is in our tasks mems_allowed, yes. If the task has been
* OOM killed and has access to memory reserves as specified by the
* TIF_MEMDIE flag, yes. Otherwise, no.
*
* The __GFP_THISNODE placement logic is really handled elsewhere,
* by forcibly using a zonelist starting at a specified node, and by
* (in get_page_from_freelist()) refusing to consider the zones for
* any node on the zonelist except the first. By the time any such
* calls get to this routine, we should just shut up and say 'yes'.
*
* Unlike the cpuset_zone_allowed_softwall() variant, above,
* this variant requires that the zone be in the current tasks
* mems_allowed or that we're in interrupt. It does not scan up the
* cpuset hierarchy for the nearest enclosing mem_exclusive cpuset.
* It never sleeps.
*/
int __cpuset_zone_allowed_hardwall(struct zone *z, gfp_t gfp_mask)
{
int node; /* node that zone z is on */
if (in_interrupt() || (gfp_mask & __GFP_THISNODE))
return 1;
node = zone_to_nid(z);
if (node_isset(node, current->mems_allowed))
return 1;
/*
* Allow tasks that have access to memory reserves because they have
* been OOM killed to get memory anywhere.
*/
if (unlikely(test_thread_flag(TIF_MEMDIE)))
return 1;
return 0;
}
/**
* cpuset_lock - lock out any changes to cpuset structures
*
* The out of memory (oom) code needs to mutex_lock cpusets
* from being changed while it scans the tasklist looking for a
* task in an overlapping cpuset. Expose callback_mutex via this
* cpuset_lock() routine, so the oom code can lock it, before
* locking the task list. The tasklist_lock is a spinlock, so
* must be taken inside callback_mutex.
*/
void cpuset_lock(void)
{
mutex_lock(&callback_mutex);
}
/**
* cpuset_unlock - release lock on cpuset changes
*
* Undo the lock taken in a previous cpuset_lock() call.
*/
void cpuset_unlock(void)
{
mutex_unlock(&callback_mutex);
}
/**
* cpuset_mem_spread_node() - On which node to begin search for a page
*
* If a task is marked PF_SPREAD_PAGE or PF_SPREAD_SLAB (as for
* tasks in a cpuset with is_spread_page or is_spread_slab set),
* and if the memory allocation used cpuset_mem_spread_node()
* to determine on which node to start looking, as it will for
* certain page cache or slab cache pages such as used for file
* system buffers and inode caches, then instead of starting on the
* local node to look for a free page, rather spread the starting
* node around the tasks mems_allowed nodes.
*
* We don't have to worry about the returned node being offline
* because "it can't happen", and even if it did, it would be ok.
*
* The routines calling guarantee_online_mems() are careful to
* only set nodes in task->mems_allowed that are online. So it
* should not be possible for the following code to return an
* offline node. But if it did, that would be ok, as this routine
* is not returning the node where the allocation must be, only
* the node where the search should start. The zonelist passed to
* __alloc_pages() will include all nodes. If the slab allocator
* is passed an offline node, it will fall back to the local node.
* See kmem_cache_alloc_node().
*/
int cpuset_mem_spread_node(void)
{
int node;
node = next_node(current->cpuset_mem_spread_rotor, current->mems_allowed);
if (node == MAX_NUMNODES)
node = first_node(current->mems_allowed);
current->cpuset_mem_spread_rotor = node;
return node;
}
EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);
/**
* cpuset_mems_allowed_intersects - Does @tsk1's mems_allowed intersect @tsk2's?
* @tsk1: pointer to task_struct of some task.
* @tsk2: pointer to task_struct of some other task.
*
* Description: Return true if @tsk1's mems_allowed intersects the
* mems_allowed of @tsk2. Used by the OOM killer to determine if
* one of the task's memory usage might impact the memory available
* to the other.
**/
int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
const struct task_struct *tsk2)
{
return nodes_intersects(tsk1->mems_allowed, tsk2->mems_allowed);
}
/*
* Collection of memory_pressure is suppressed unless
* this flag is enabled by writing "1" to the special
* cpuset file 'memory_pressure_enabled' in the root cpuset.
*/
int cpuset_memory_pressure_enabled __read_mostly;
/**
* cpuset_memory_pressure_bump - keep stats of per-cpuset reclaims.
*
* Keep a running average of the rate of synchronous (direct)
* page reclaim efforts initiated by tasks in each cpuset.
*
* This represents the rate at which some task in the cpuset
* ran low on memory on all nodes it was allowed to use, and
* had to enter the kernels page reclaim code in an effort to
* create more free memory by tossing clean pages or swapping
* or writing dirty pages.
*
* Display to user space in the per-cpuset read-only file
* "memory_pressure". Value displayed is an integer
* representing the recent rate of entry into the synchronous
* (direct) page reclaim by any task attached to the cpuset.
**/
void __cpuset_memory_pressure_bump(void)
{
task_lock(current);
fmeter_markevent(&task_cs(current)->fmeter);
task_unlock(current);
}
#ifdef CONFIG_PROC_PID_CPUSET
/*
* proc_cpuset_show()
* - Print tasks cpuset path into seq_file.
* - Used for /proc/<pid>/cpuset.
* - No need to task_lock(tsk) on this tsk->cpuset reference, as it
* doesn't really matter if tsk->cpuset changes after we read it,
* and we take manage_mutex, keeping attach_task() from changing it
* anyway. No need to check that tsk->cpuset != NULL, thanks to
* the_top_cpuset_hack in cpuset_exit(), which sets an exiting tasks
* cpuset to top_cpuset.
*/
static int proc_cpuset_show(struct seq_file *m, void *unused_v)
{
struct pid *pid;
struct task_struct *tsk;
char *buf;
struct cgroup_subsys_state *css;
int retval;
retval = -ENOMEM;
buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!buf)
goto out;
retval = -ESRCH;
pid = m->private;
tsk = get_pid_task(pid, PIDTYPE_PID);
if (!tsk)
goto out_free;
retval = -EINVAL;
cgroup_lock();
css = task_subsys_state(tsk, cpuset_subsys_id);
retval = cgroup_path(css->cgroup, buf, PAGE_SIZE);
if (retval < 0)
goto out_unlock;
seq_puts(m, buf);
seq_putc(m, '\n');
out_unlock:
cgroup_unlock();
put_task_struct(tsk);
out_free:
kfree(buf);
out:
return retval;
}
static int cpuset_open(struct inode *inode, struct file *file)
{
struct pid *pid = PROC_I(inode)->pid;
return single_open(file, proc_cpuset_show, pid);
}
const struct file_operations proc_cpuset_operations = {
.open = cpuset_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
#endif /* CONFIG_PROC_PID_CPUSET */
/* Display task cpus_allowed, mems_allowed in /proc/<pid>/status file. */
char *cpuset_task_status_allowed(struct task_struct *task, char *buffer)
{
buffer += sprintf(buffer, "Cpus_allowed:\t");
buffer += cpumask_scnprintf(buffer, PAGE_SIZE, task->cpus_allowed);
buffer += sprintf(buffer, "\n");
buffer += sprintf(buffer, "Mems_allowed:\t");
buffer += nodemask_scnprintf(buffer, PAGE_SIZE, task->mems_allowed);
buffer += sprintf(buffer, "\n");
return buffer;
}
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