| /* |
| * 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; |
| /* 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); |
| } |