The patch titled
Subject: mm, oom: avoid printk() iteration under RCU
has been added to the -mm tree. Its filename is
mm-oom-avoid-printk-iteration-under-rcu.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-oom-avoid-printk-iteration-under-rcu.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-oom-avoid-printk-iteration-under-rcu.patch
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------------------------------------------------------
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Subject: mm, oom: avoid printk() iteration under RCU
Currently dump_tasks() might call printk() for many thousands times under
RCU, which might take many minutes for slow consoles. Therefore, split
dump_tasks() into three stages; take a snapshot of possible OOM victim
candidates under RCU, dump the snapshot from reschedulable context, and
destroy the snapshot.
In a future patch, the first stage would be moved to select_bad_process()
and the third stage would be moved to after oom_kill_process(), and will
simplify refcount handling.
Link: http://lkml.kernel.org/r/1563360901-8277-1-git-send-email-penguin-kernel@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched.h | 1
mm/oom_kill.c | 67 +++++++++++++++++++---------------------
2 files changed, 34 insertions(+), 34 deletions(-)
--- a/include/linux/sched.h~mm-oom-avoid-printk-iteration-under-rcu
+++ a/include/linux/sched.h
@@ -1246,6 +1246,7 @@ struct task_struct {
#ifdef CONFIG_MMU
struct task_struct *oom_reaper_list;
#endif
+ struct list_head oom_victim_list;
#ifdef CONFIG_VMAP_STACK
struct vm_struct *stack_vm_area;
#endif
--- a/mm/oom_kill.c~mm-oom-avoid-printk-iteration-under-rcu
+++ a/mm/oom_kill.c
@@ -377,36 +377,13 @@ static void select_bad_process(struct oo
}
}
-static int dump_task(struct task_struct *p, void *arg)
-{
- struct oom_control *oc = arg;
- struct task_struct *task;
-
- if (oom_unkillable_task(p))
- return 0;
- /* p may not have freeable memory in nodemask */
- if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
- return 0;
-
- task = find_lock_task_mm(p);
- if (!task) {
- /*
- * This is a kthread or all of p's threads have already
- * detached their mm's. There's no need to report
- * them; they can't be oom killed anyway.
- */
- return 0;
+static int add_candidate_task(struct task_struct *p, void *arg)
+{
+ if (!oom_unkillable_task(p)) {
+ get_task_struct(p);
+ list_add_tail(&p->oom_victim_list, (struct list_head *) arg);
}
-
- pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n",
- task->pid, from_kuid(&init_user_ns, task_uid(task)),
- task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
- mm_pgtables_bytes(task->mm),
- get_mm_counter(task->mm, MM_SWAPENTS),
- task->signal->oom_score_adj, task->comm);
- task_unlock(task);
-
return 0;
}
@@ -422,19 +399,41 @@ static int dump_task(struct task_struct
*/
static void dump_tasks(struct oom_control *oc)
{
- pr_info("Tasks state (memory values in pages):\n");
- pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n");
+ static LIST_HEAD(list);
+ struct task_struct *p;
+ struct task_struct *t;
if (is_memcg_oom(oc))
- mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
+ mem_cgroup_scan_tasks(oc->memcg, add_candidate_task, &list);
else {
- struct task_struct *p;
-
rcu_read_lock();
for_each_process(p)
- dump_task(p, oc);
+ add_candidate_task(p, &list);
rcu_read_unlock();
}
+ pr_info("Tasks state (memory values in pages):\n");
+ pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n");
+ list_for_each_entry(p, &list, oom_victim_list) {
+ cond_resched();
+ /* p may not have freeable memory in nodemask */
+ if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
+ continue;
+ /* All of p's threads might have already detached their mm's. */
+ t = find_lock_task_mm(p);
+ if (!t)
+ continue;
+ pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n",
+ t->pid, from_kuid(&init_user_ns, task_uid(t)),
+ t->tgid, t->mm->total_vm, get_mm_rss(t->mm),
+ mm_pgtables_bytes(t->mm),
+ get_mm_counter(t->mm, MM_SWAPENTS),
+ t->signal->oom_score_adj, t->comm);
+ task_unlock(t);
+ }
+ list_for_each_entry_safe(p, t, &list, oom_victim_list) {
+ list_del(&p->oom_victim_list);
+ put_task_struct(p);
+ }
}
static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim)
_
Patches currently in -mm which might be from penguin-kernel@xxxxxxxxxxxxxxxxxxx are
mm-oom-avoid-printk-iteration-under-rcu.patch
info-task-hung-in-generic_file_write_iter.patch
info-task-hung-in-generic_file_write-fix.patch
kexec-bail-out-upon-sigkill-when-allocating-memory.patch
