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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /mm/oom_kill.c | |
download | op-kernel-dev-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.zip op-kernel-dev-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'mm/oom_kill.c')
-rw-r--r-- | mm/oom_kill.c | 292 |
1 files changed, 292 insertions, 0 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c new file mode 100644 index 0000000..9595a0f --- /dev/null +++ b/mm/oom_kill.c @@ -0,0 +1,292 @@ +/* + * 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 kswapd() + * in linux/mm/vmscan.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> + +/* #define DEBUG */ + +/** + * oom_badness - calculate a numeric value for how bad this task has been + * @p: task struct of which task we should calculate + * @p: 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 childs if they + * have an own mm. This prevents forking servers to flood the + * machine with an endless amount of childs + */ + 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) + /* skip the init task with pid == 1 */ + if (p->pid > 1) { + unsigned long points; + + /* + * This is in the process of releasing memory so wait it + * to finish before killing some other task by mistake. + */ + if ((unlikely(test_tsk_thread_flag(p, TIF_MEMDIE)) || (p->flags & PF_EXITING)) && + !(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(unsigned int __nocast gfp_mask) +{ + struct mm_struct *mm = NULL; + task_t * p; + + 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); + show_free_areas(); + panic("Out of memory and no killable processes...\n"); + } + + printk("oom-killer: gfp_mask=0x%x\n", gfp_mask); + show_free_areas(); + 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. + */ + __set_current_state(TASK_INTERRUPTIBLE); + schedule_timeout(1); +} |