/* * linux/mm/oom_kill.c * * Copyright (C) 1998,2000 Rik van Riel * Thanks go out to Claus Fischer for some serious inspiration and * for goading me into coding this file... * * The routines in this file are used to kill a process when * we're seriously out of memory. This gets called from __alloc_pages() * in mm/page_alloc.c when we really run out of memory. * * Since we won't call these routines often (on a well-configured * machine) this file will double as a 'coding guide' and a signpost * for newbie kernel hackers. It features several pointers to major * kernel subsystems and hints as to where to find out what things do. */ #include <linux/oom.h>#include <linux/mm.h>#include <linux/sched.h>#include <linux/swap.h>#include <linux/timex.h>#include <linux/jiffies.h>#include <linux/cpuset.h>#include <linux/module.h>#include <linux/notifier.h> int sysctl_panic_on_oom;/* #define DEBUG */ /** * badness - calculate a numeric value for how bad this task has been * @p: task struct of which task we should calculate * @uptime: current uptime in seconds * * The formula used is relatively simple and documented inline in the * function. The main rationale is that we want to select a good task * to kill when we run out of memory. * * Good in this context means that: * 1) we lose the minimum amount of work done * 2) we recover a large amount of memory * 3) we don't kill anything innocent of eating tons of memory * 4) we want to kill the minimum amount of processes (one) * 5) we try to kill the process the user expects us to kill, this * algorithm has been meticulously tuned to meet the principle * of least surprise ... (be careful when you change it) */ unsigned long badness(struct task_struct *p, unsigned long uptime){ unsigned long points, cpu_time, run_time, s; struct mm_struct *mm; struct task_struct *child; task_lock(p); mm = p->mm; if (!mm) { task_unlock(p); return 0; } /* * The memory size of the process is the basis for the badness. */ points = mm->total_vm; /* * After this unlock we can no longer dereference local variable `mm' */ task_unlock(p); /* * swapoff can easily use up all memory, so kill those first. */ if (p->flags & PF_SWAPOFF) return ULONG_MAX; /* * Processes which fork a lot of child processes are likely * a good choice. We add half the vmsize of the children if they * have an own mm. This prevents forking servers to flood the * machine with an endless amount of children. In case a single * child is eating the vast majority of memory, adding only half * to the parents will make the child our kill candidate of choice. */ list_for_each_entry(child, &p->children, sibling) { task_lock(child); if (child->mm != mm && child->mm) points += child->mm->total_vm/2 + 1; task_unlock(child); } /* * CPU time is in tens of seconds and run time is in thousands * of seconds. There is no particular reason for this other than * that it turned out to work very well in practice. */ cpu_time = (cputime_to_jiffies(p->utime) + cputime_to_jiffies(p->stime)) >> (SHIFT_HZ + 3); if (uptime >= p->start_time.tv_sec) run_time = (uptime - p->start_time.tv_sec) >> 10; else run_time = 0; s = int_sqrt(cpu_time); if (s) points /= s; s = int_sqrt(int_sqrt(run_time)); if (s) points /= s; /* * Niced processes are most likely less important, so double * their badness points. */ if (task_nice(p) > 0) points *= 2; /* * Superuser processes are usually more important, so we make it * less likely that we kill those. */ if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_ADMIN) || p->uid == 0 || p->euid == 0) points /= 4; /* * We don't want to kill a process with direct hardware access. * Not only could that mess up the hardware, but usually users * tend to only have this flag set on applications they think * of as important. */ if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_RAWIO)) points /= 4; /* * If p's nodes don't overlap ours, it may still help to kill p * because p may have allocated or otherwise mapped memory on * this node before. However it will be less likely. */ if (!cpuset_excl_nodes_overlap(p)) points /= 8; /* * Adjust the score by oomkilladj. */ if (p->oomkilladj) { if (p->oomkilladj > 0) points <<= p->oomkilladj; else points >>= -(p->oomkilladj); } #ifdef DEBUG printk(KERN_DEBUG "OOMkill: task %d (%s) got %d points\n", p->pid, p->comm, points);#endif return points;} /* * Types of limitations to the nodes from which allocations may occur */#define CONSTRAINT_NONE 1#define CONSTRAINT_MEMORY_POLICY 2#define CONSTRAINT_CPUSET 3 /* * Determine the type of allocation constraint. */static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask){#ifdef CONFIG_NUMA struct zone **z; nodemask_t nodes; int node; nodes_clear(nodes); /* node has memory ? */ for_each_online_node(node) if (NODE_DATA(node)->node_present_pages) node_set(node, nodes); for (z = zonelist->zones; *z; z++) if (cpuset_zone_allowed_softwall(*z, gfp_mask)) node_clear(zone_to_nid(*z), nodes); else return CONSTRAINT_CPUSET; if (!nodes_empty(nodes)) return CONSTRAINT_MEMORY_POLICY;#endif return CONSTRAINT_NONE;} /* * Simple selection loop. We chose the process with the highest * number of 'points'. We expect the caller will lock the tasklist. * * (not docbooked, we don't want this one cluttering up the manual) */static struct task_struct *select_bad_process(unsigned long *ppoints){ struct task_struct *g, *p; struct task_struct *chosen = NULL; struct timespec uptime; *ppoints = 0; do_posix_clock_monotonic_gettime(&uptime); do_each_thread(g, p) { unsigned long points; /* * skip kernel threads and tasks which have already released * their mm. */ if (!p->mm) continue; /* skip the init task */ if (is_init(p)) continue; /* * This task already has access to memory reserves and is * being killed. Don't allow any other task access to the * memory reserve. * * Note: this may have a chance of deadlock if it gets * blocked waiting for another task which itself is waiting * for memory. Is there a better alternative? */ if (test_tsk_thread_flag(p, TIF_MEMDIE)) return ERR_PTR(-1UL); /* * This is in the process of releasing memory so wait for it * to finish before killing some other task by mistake. * * However, if p is the current task, we allow the 'kill' to * go ahead if it is exiting: this will simply set TIF_MEMDIE, * which will allow it to gain access to memory reserves in * the process of exiting and releasing its resources. * Otherwise we could get an easy OOM deadlock. */ if (p->flags & PF_EXITING) { if (p != current) return ERR_PTR(-1UL); chosen = p; *ppoints = ULONG_MAX; } if (p->oomkilladj == OOM_DISABLE) continue; points = badness(p, uptime.tv_sec); if (points > *ppoints || !chosen) { chosen = p; *ppoints = points; } } while_each_thread(g, p); return chosen;} /** * Send SIGKILL to the selected process irrespective of CAP_SYS_RAW_IO * flag though it's unlikely that we select a process with CAP_SYS_RAW_IO * set. */static void __oom_kill_task(struct task_struct *p, int verbose){ if (is_init(p)) { WARN_ON(1); printk(KERN_WARNING "tried to kill init!\n"); return; } if (!p->mm) { WARN_ON(1); printk(KERN_WARNING "tried to kill an mm-less task!\n"); return; } if (verbose) printk(KERN_ERR "Killed process %d (%s)\n", p->pid, p->comm); /* * We give our sacrificial lamb high priority and access to * all the memory it needs. That way it should be able to * exit() and clear out its resources quickly... */ p->time_slice = HZ; set_tsk_thread_flag(p, TIF_MEMDIE); force_sig(SIGKILL, p);} static int oom_kill_task(struct task_struct *p){ struct mm_struct *mm; struct task_struct *g, *q; mm = p->mm; /* WARNING: mm may not be dereferenced since we did not obtain its * value from get_task_mm(p). This is OK since all we need to do is * compare mm to q->mm below. * * Furthermore, even if mm contains a non-NULL value, p->mm may * change to NULL at any time since we do not hold task_lock(p). * However, this is of no concern to us. */ if (mm == NULL) return 1; /* * Don't kill the process if any threads are set to OOM_DISABLE */ do_each_thread(g, q) { if (q->mm == mm && q->oomkilladj == OOM_DISABLE) return 1; } while_each_thread(g, q); __oom_kill_task(p, 1); /* * kill all processes that share the ->mm (i.e. all threads), * but are in a different thread group. Don't let them have access * to memory reserves though, otherwise we might deplete all memory. */ do_each_thread(g, q) { if (q->mm == mm && q->tgid != p->tgid) force_sig(SIGKILL, q); } while_each_thread(g, q); return 0;} static int oom_kill_process(struct task_struct *p, unsigned long points, const char *message){ struct task_struct *c; struct list_head *tsk; /* * If the task is already exiting, don't alarm the sysadmin or kill * its children or threads, just set TIF_MEMDIE so it can die quickly */ if (p->flags & PF_EXITING) { __oom_kill_task(p, 0); return 0; } printk(KERN_ERR "%s: kill process %d (%s) score %li or a child\n", message, p->pid, p->comm, points); /* Try to kill a child first */ list_for_each(tsk, &p->children) { c = list_entry(tsk, struct task_struct, sibling); if (c->mm == p->mm) continue; if (!oom_kill_task(c)) return 0; } return oom_kill_task(p);} static BLOCKING_NOTIFIER_HEAD(oom_notify_list); int register_oom_notifier(struct notifier_block *nb){ return blocking_notifier_chain_register(&oom_notify_list, nb);}EXPORT_SYMBOL_GPL(register_oom_notifier); int unregister_oom_notifier(struct notifier_block *nb){ return blocking_notifier_chain_unregister(&oom_notify_list, nb);}EXPORT_SYMBOL_GPL(unregister_oom_notifier); /** * out_of_memory - kill the "best" process when we run out of memory * * If we run out of memory, we have the choice between either * killing a random task (bad), letting the system crash (worse) * OR try to be smart about which process to kill. Note that we * don't have to be perfect here, we just have to be good. */void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order){ struct task_struct *p; unsigned long points = 0; unsigned long freed = 0; blocking_notifier_call_chain(&oom_notify_list, 0, &freed); if (freed > 0) /* Got some memory back in the last second. */ return; if (printk_ratelimit()) { printk(KERN_WARNING "%s invoked oom-killer: " "gfp_mask=0x%x, order=%d, oomkilladj=%d\n", current->comm, gfp_mask, order, current->oomkilladj); dump_stack(); show_mem(); } cpuset_lock(); read_lock(&tasklist_lock); /* * Check if there were limitations on the allocation (only relevant for * NUMA) that may require different handling. */ switch (constrained_alloc(zonelist, gfp_mask)) { case CONSTRAINT_MEMORY_POLICY: oom_kill_process(current, points, "No available memory (MPOL_BIND)"); break; case CONSTRAINT_CPUSET: oom_kill_process(current, points, "No available memory in cpuset"); break; case CONSTRAINT_NONE: if (sysctl_panic_on_oom) panic("out of memory. panic_on_oom is selected\n");retry: /* * Rambo mode: Shoot down a process and hope it solves whatever * issues we may have. */ p = select_bad_process(&points); if (PTR_ERR(p) == -1UL) goto out; /* Found nothing?!?! Either we hang forever, or we panic. */ if (!p) { read_unlock(&tasklist_lock); cpuset_unlock(); panic("Out of memory and no killable processes...\n"); } if (oom_kill_process(p, points, "Out of memory")) goto retry; break; } out: read_unlock(&tasklist_lock); cpuset_unlock(); /* * Give "p" a good chance of killing itself before we * retry to allocate memory unless "p" is current */ if (!test_thread_flag(TIF_MEMDIE)) schedule_timeout_uninterruptible(1);}
/*
* linux/mm/oom_kill.c
*
* Copyright (C) 1998,2000 Rik van Riel
* Thanks go out to Claus Fischer for some serious inspiration and
* for goading me into coding this file...
*
* The routines in this file are used to kill a process when
* we're seriously out of memory. This gets called from __alloc_pages()
* in mm/page_alloc.c when we really run out of memory.
*
* Since we won't call these routines often (on a well-configured
* machine) this file will double as a 'coding guide' and a signpost
* for newbie kernel hackers. It features several pointers to major
* kernel subsystems and hints as to where to find out what things do.
*/
#include <linux/oom.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/swap.h>
#include <linux/timex.h>
#include <linux/jiffies.h>
#include <linux/cpuset.h>
#include <linux/module.h>
#include <linux/notifier.h>
int sysctl_panic_on_oom;
/* #define DEBUG */
/**
* badness - calculate a numeric value for how bad this task has been
* @p: task struct of which task we should calculate
* @uptime: current uptime in seconds
*
* The formula used is relatively simple and documented inline in the
* function. The main rationale is that we want to select a good task
* to kill when we run out of memory.
*
* Good in this context means that:
* 1) we lose the minimum amount of work done
* 2) we recover a large amount of memory
* 3) we don't kill anything innocent of eating tons of memory
* 4) we want to kill the minimum amount of processes (one)
* 5) we try to kill the process the user expects us to kill, this
* algorithm has been meticulously tuned to meet the principle
* of least surprise ... (be careful when you change it)
*/
unsigned long badness(struct task_struct *p, unsigned long uptime)
{
unsigned long points, cpu_time, run_time, s;
struct mm_struct *mm;
struct task_struct *child;
task_lock(p);
mm = p->mm;
if (!mm) {
task_unlock(p);
return 0;
}
/*
* The memory size of the process is the basis for the badness.
*/
points = mm->total_vm;
/*
* After this unlock we can no longer dereference local variable `mm'
*/
task_unlock(p);
/*
* swapoff can easily use up all memory, so kill those first.
*/
if (p->flags & PF_SWAPOFF)
return ULONG_MAX;
/*
* Processes which fork a lot of child processes are likely
* a good choice. We add half the vmsize of the children if they
* have an own mm. This prevents forking servers to flood the
* machine with an endless amount of children. In case a single
* child is eating the vast majority of memory, adding only half
* to the parents will make the child our kill candidate of choice.
*/
list_for_each_entry(child, &p->children, sibling) {
task_lock(child);
if (child->mm != mm && child->mm)
points += child->mm->total_vm/2 + 1;
task_unlock(child);
}
/*
* CPU time is in tens of seconds and run time is in thousands
* of seconds. There is no particular reason for this other than
* that it turned out to work very well in practice.
*/
cpu_time = (cputime_to_jiffies(p->utime) + cputime_to_jiffies(p->stime))
>> (SHIFT_HZ + 3);
if (uptime >= p->start_time.tv_sec)
run_time = (uptime - p->start_time.tv_sec) >> 10;
else
run_time = 0;
s = int_sqrt(cpu_time);
if (s)
points /= s;
s = int_sqrt(int_sqrt(run_time));
if (s)
points /= s;
/*
* Niced processes are most likely less important, so double
* their badness points.
*/
if (task_nice(p) > 0)
points *= 2;
/*
* Superuser processes are usually more important, so we make it
* less likely that we kill those.
*/
if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_ADMIN) ||
p->uid == 0 || p->euid == 0)
points /= 4;
/*
* We don't want to kill a process with direct hardware access.
* Not only could that mess up the hardware, but usually users
* tend to only have this flag set on applications they think
* of as important.
*/
if (cap_t(p->cap_effective) & CAP_TO_MASK(CAP_SYS_RAWIO))
points /= 4;
/*
* If p's nodes don't overlap ours, it may still help to kill p
* because p may have allocated or otherwise mapped memory on
* this node before. However it will be less likely.
*/
if (!cpuset_excl_nodes_overlap(p))
points /= 8;
/*
* Adjust the score by oomkilladj.
*/
if (p->oomkilladj) {
if (p->oomkilladj > 0)
points <<= p->oomkilladj;
else
points >>= -(p->oomkilladj);
}
#ifdef DEBUG
printk(KERN_DEBUG "OOMkill: task %d (%s) got %d points\n",
p->pid, p->comm, points);
#endif
return points;
}
/*
* Types of limitations to the nodes from which allocations may occur
*/
#define CONSTRAINT_NONE 1
#define CONSTRAINT_MEMORY_POLICY 2
#define CONSTRAINT_CPUSET 3
/*
* Determine the type of allocation constraint.
*/
static inline int constrained_alloc(struct zonelist *zonelist, gfp_t gfp_mask)
{
#ifdef CONFIG_NUMA
struct zone **z;
nodemask_t nodes;
int node;
nodes_clear(nodes);
/* node has memory ? */
for_each_online_node(node)
if (NODE_DATA(node)->node_present_pages)
node_set(node, nodes);
for (z = zonelist->zones; *z; z++)
if (cpuset_zone_allowed_softwall(*z, gfp_mask))
node_clear(zone_to_nid(*z), nodes);
else
return CONSTRAINT_CPUSET;
if (!nodes_empty(nodes))
return CONSTRAINT_MEMORY_POLICY;
#endif
return CONSTRAINT_NONE;
}
/*
* Simple selection loop. We chose the process with the highest
* number of 'points'. We expect the caller will lock the tasklist.
*
* (not docbooked, we don't want this one cluttering up the manual)
*/
static struct task_struct *select_bad_process(unsigned long *ppoints)
{
struct task_struct *g, *p;
struct task_struct *chosen = NULL;
struct timespec uptime;
*ppoints = 0;
do_posix_clock_monotonic_gettime(&uptime);
do_each_thread(g, p) {
unsigned long points;
/*
* skip kernel threads and tasks which have already released
* their mm.
*/
if (!p->mm)
continue;
/* skip the init task */
if (is_init(p))
continue;
/*
* This task already has access to memory reserves and is
* being killed. Don't allow any other task access to the
* memory reserve.
*
* Note: this may have a chance of deadlock if it gets
* blocked waiting for another task which itself is waiting
* for memory. Is there a better alternative?
*/
if (test_tsk_thread_flag(p, TIF_MEMDIE))
return ERR_PTR(-1UL);
/*
* This is in the process of releasing memory so wait for it
* to finish before killing some other task by mistake.
*
* However, if p is the current task, we allow the 'kill' to
* go ahead if it is exiting: this will simply set TIF_MEMDIE,
* which will allow it to gain access to memory reserves in
* the process of exiting and releasing its resources.
* Otherwise we could get an easy OOM deadlock.
*/
if (p->flags & PF_EXITING) {
if (p != current)
return ERR_PTR(-1UL);
chosen = p;
*ppoints = ULONG_MAX;
}
if (p->oomkilladj == OOM_DISABLE)
continue;
points = badness(p, uptime.tv_sec);
if (points > *ppoints || !chosen) {
chosen = p;
*ppoints = points;
}
} while_each_thread(g, p);
return chosen;
}
/**
* Send SIGKILL to the selected process irrespective of CAP_SYS_RAW_IO
* flag though it's unlikely that we select a process with CAP_SYS_RAW_IO
* set.
*/
static void __oom_kill_task(struct task_struct *p, int verbose)
{
if (is_init(p)) {
WARN_ON(1);
printk(KERN_WARNING "tried to kill init!\n");
return;
}
if (!p->mm) {
WARN_ON(1);
printk(KERN_WARNING "tried to kill an mm-less task!\n");
return;
}
if (verbose)
printk(KERN_ERR "Killed process %d (%s)\n", p->pid, p->comm);
/*
* We give our sacrificial lamb high priority and access to
* all the memory it needs. That way it should be able to
* exit() and clear out its resources quickly...
*/
p->time_slice = HZ;
set_tsk_thread_flag(p, TIF_MEMDIE);
force_sig(SIGKILL, p);
}
static int oom_kill_task(struct task_struct *p)
{
struct mm_struct *mm;
struct task_struct *g, *q;
mm = p->mm;
/* WARNING: mm may not be dereferenced since we did not obtain its
* value from get_task_mm(p). This is OK since all we need to do is
* compare mm to q->mm below.
*
* Furthermore, even if mm contains a non-NULL value, p->mm may
* change to NULL at any time since we do not hold task_lock(p).
* However, this is of no concern to us.
*/
if (mm == NULL)
return 1;
/*
* Don't kill the process if any threads are set to OOM_DISABLE
*/
do_each_thread(g, q) {
if (q->mm == mm && q->oomkilladj == OOM_DISABLE)
return 1;
} while_each_thread(g, q);
__oom_kill_task(p, 1);
/*
* kill all processes that share the ->mm (i.e. all threads),
* but are in a different thread group. Don't let them have access
* to memory reserves though, otherwise we might deplete all memory.
*/
do_each_thread(g, q) {
if (q->mm == mm && q->tgid != p->tgid)
force_sig(SIGKILL, q);
} while_each_thread(g, q);
return 0;
}
static int oom_kill_process(struct task_struct *p, unsigned long points,
const char *message)
{
struct task_struct *c;
struct list_head *tsk;
/*
* If the task is already exiting, don't alarm the sysadmin or kill
* its children or threads, just set TIF_MEMDIE so it can die quickly
*/
if (p->flags & PF_EXITING) {
__oom_kill_task(p, 0);
return 0;
}
printk(KERN_ERR "%s: kill process %d (%s) score %li or a child\n",
message, p->pid, p->comm, points);
/* Try to kill a child first */
list_for_each(tsk, &p->children) {
c = list_entry(tsk, struct task_struct, sibling);
if (c->mm == p->mm)
continue;
if (!oom_kill_task(c))
return 0;
}
return oom_kill_task(p);
}
static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
int register_oom_notifier(struct notifier_block *nb)
{
return blocking_notifier_chain_register(&oom_notify_list, nb);
}
EXPORT_SYMBOL_GPL(register_oom_notifier);
int unregister_oom_notifier(struct notifier_block *nb)
{
return blocking_notifier_chain_unregister(&oom_notify_list, nb);
}
EXPORT_SYMBOL_GPL(unregister_oom_notifier);
/**
* out_of_memory - kill the "best" process when we run out of memory
*
* If we run out of memory, we have the choice between either
* killing a random task (bad), letting the system crash (worse)
* OR try to be smart about which process to kill. Note that we
* don't have to be perfect here, we just have to be good.
*/
void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
{
struct task_struct *p;
unsigned long points = 0;
unsigned long freed = 0;
blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
if (freed > 0)
/* Got some memory back in the last second. */
return;
if (printk_ratelimit()) {
printk(KERN_WARNING "%s invoked oom-killer: "
"gfp_mask=0x%x, order=%d, oomkilladj=%d\n",
current->comm, gfp_mask, order, current->oomkilladj);
dump_stack();
show_mem();
}
cpuset_lock();
read_lock(&tasklist_lock);
/*
* Check if there were limitations on the allocation (only relevant for
* NUMA) that may require different handling.
*/
switch (constrained_alloc(zonelist, gfp_mask)) {
case CONSTRAINT_MEMORY_POLICY:
oom_kill_process(current, points,
"No available memory (MPOL_BIND)");
break;
case CONSTRAINT_CPUSET:
oom_kill_process(current, points,
"No available memory in cpuset");
break;
case CONSTRAINT_NONE:
if (sysctl_panic_on_oom)
panic("out of memory. panic_on_oom is selected\n");
retry:
/*
* Rambo mode: Shoot down a process and hope it solves whatever
* issues we may have.
*/
p = select_bad_process(&points);
if (PTR_ERR(p) == -1UL)
goto out;
/* Found nothing?!?! Either we hang forever, or we panic. */
if (!p) {
read_unlock(&tasklist_lock);
cpuset_unlock();
panic("Out of memory and no killable processes...\n");
}
if (oom_kill_process(p, points, "Out of memory"))
goto retry;
break;
}
out:
read_unlock(&tasklist_lock);
cpuset_unlock();
/*
* Give "p" a good chance of killing itself before we
* retry to allocate memory unless "p" is current
*/
if (!test_thread_flag(TIF_MEMDIE))
schedule_timeout_uninterruptible(1);
}