[ups, I've cut the Cc list somehow, sorry about that] On Wed 24-07-19 08:27:27, Michal Hocko wrote: > Andrew, > I've had some concerns wrt. this patch - especially the additional > complexity - and I have to say I am not convinced that this is really > needed. Our past experience in this area suggests that more tricky code > leads to different corner cases. So I am really reluctant to add more > complexity without any real world reports. > > On Tue 23-07-19 16:14:29, Andrew Morton wrote: > > From: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> > > 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-ker...@i-love.sakura.ne.jp > > Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> > > Cc: Shakeel Butt <shake...@google.com> > > Cc: Michal Hocko <mho...@suse.com> > > Cc: Roman Gushchin <g...@fb.com> > > Cc: David Rientjes <rient...@google.com> > > Signed-off-by: Andrew Morton <a...@linux-foundation.org> > > --- > > > > 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-ker...@i-love.sakura.ne.jp 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 > > -- > Michal Hocko > SUSE Labs
-- Michal Hocko SUSE Labs
