linux/mm/oom_kill.c
Al Viro dd0fc66fb3 [PATCH] gfp flags annotations - part 1
- added typedef unsigned int __nocast gfp_t;

 - replaced __nocast uses for gfp flags with gfp_t - it gives exactly
   the same warnings as far as sparse is concerned, doesn't change
   generated code (from gcc point of view we replaced unsigned int with
   typedef) and documents what's going on far better.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-08 15:00:57 -07:00

305 lines
7.6 KiB
C

/*
* 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/mm.h>
#include <linux/sched.h>
#include <linux/swap.h>
#include <linux/timex.h>
#include <linux/jiffies.h>
#include <linux/cpuset.h>
/* #define DEBUG */
/**
* oom_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 list_head *tsk;
if (!p->mm)
return 0;
/*
* The memory size of the process is the basis for the badness.
*/
points = p->mm->total_vm;
/*
* Processes which fork a lot of child processes are likely
* a good choice. We add 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
*/
list_for_each(tsk, &p->children) {
struct task_struct *chld;
chld = list_entry(tsk, struct task_struct, sibling);
if (chld->mm != p->mm && chld->mm)
points += chld->mm->total_vm;
}
/*
* 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;
/*
* 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;
}
/*
* 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(void)
{
unsigned long maxpoints = 0;
struct task_struct *g, *p;
struct task_struct *chosen = NULL;
struct timespec uptime;
do_posix_clock_monotonic_gettime(&uptime);
do_each_thread(g, p) {
unsigned long points;
int releasing;
/* skip the init task with pid == 1 */
if (p->pid == 1)
continue;
if (p->oomkilladj == OOM_DISABLE)
continue;
/* If p's nodes don't overlap ours, it won't help to kill p. */
if (!cpuset_excl_nodes_overlap(p))
continue;
/*
* This is in the process of releasing memory so for wait it
* to finish before killing some other task by mistake.
*/
releasing = test_tsk_thread_flag(p, TIF_MEMDIE) ||
p->flags & PF_EXITING;
if (releasing && !(p->flags & PF_DEAD))
return ERR_PTR(-1UL);
if (p->flags & PF_SWAPOFF)
return p;
points = badness(p, uptime.tv_sec);
if (points > maxpoints || !chosen) {
chosen = p;
maxpoints = points;
}
} while_each_thread(g, p);
return chosen;
}
/**
* We must be careful though to never send SIGKILL a process with
* CAP_SYS_RAW_IO set, send SIGTERM instead (but it's unlikely that
* we select a process with CAP_SYS_RAW_IO set).
*/
static void __oom_kill_task(task_t *p)
{
if (p->pid == 1) {
WARN_ON(1);
printk(KERN_WARNING "tried to kill init!\n");
return;
}
task_lock(p);
if (!p->mm || p->mm == &init_mm) {
WARN_ON(1);
printk(KERN_WARNING "tried to kill an mm-less task!\n");
task_unlock(p);
return;
}
task_unlock(p);
printk(KERN_ERR "Out of Memory: 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 struct mm_struct *oom_kill_task(task_t *p)
{
struct mm_struct *mm = get_task_mm(p);
task_t * g, * q;
if (!mm)
return NULL;
if (mm == &init_mm) {
mmput(mm);
return NULL;
}
__oom_kill_task(p);
/*
* kill all processes that share the ->mm (i.e. all threads),
* but are in a different thread group
*/
do_each_thread(g, q)
if (q->mm == mm && q->tgid != p->tgid)
__oom_kill_task(q);
while_each_thread(g, q);
return mm;
}
static struct mm_struct *oom_kill_process(struct task_struct *p)
{
struct mm_struct *mm;
struct task_struct *c;
struct list_head *tsk;
/* 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;
mm = oom_kill_task(c);
if (mm)
return mm;
}
return oom_kill_task(p);
}
/**
* oom_kill - 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(gfp_t gfp_mask, int order)
{
struct mm_struct *mm = NULL;
task_t * p;
if (printk_ratelimit()) {
printk("oom-killer: gfp_mask=0x%x, order=%d\n",
gfp_mask, order);
show_mem();
}
read_lock(&tasklist_lock);
retry:
p = select_bad_process();
if (PTR_ERR(p) == -1UL)
goto out;
/* Found nothing?!?! Either we hang forever, or we panic. */
if (!p) {
read_unlock(&tasklist_lock);
panic("Out of memory and no killable processes...\n");
}
mm = oom_kill_process(p);
if (!mm)
goto retry;
out:
read_unlock(&tasklist_lock);
if (mm)
mmput(mm);
/*
* Give "p" a good chance of killing itself before we
* retry to allocate memory.
*/
schedule_timeout_interruptible(1);
}