Messages in this thread Patch in this message | | | From | KOSAKI Motohiro <> | Subject | Re: [patch -mm v2] mm: introduce oom_adj_child | Date | Mon, 3 Aug 2009 21:16:25 +0900 (JST) |
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> On Fri, 31 Jul 2009, KOSAKI Motohiro wrote: > > > diff --git a/fs/proc/base.c b/fs/proc/base.c > > index 3ce5ae9..c64499e 100644 > > --- a/fs/proc/base.c > > +++ b/fs/proc/base.c > > @@ -1008,7 +1008,7 @@ static ssize_t oom_adjust_read(struct file *file, char __user *buf, > > return -ESRCH; > > task_lock(task); > > if (task->mm) > > - oom_adjust = task->mm->oom_adj; > > + oom_adjust = task->signal->oom_adj; > > else > > oom_adjust = OOM_DISABLE; > > task_unlock(task); > > This may display a /proc/pid/oom_adj that is radically different from > task->mm->oom_adj_cached without knowledge to userspace and you can't > simply display task->mm>oom_adj_cached here because it gets reset on every > write to /proc/pid/oom_adj.
Is this necessary? different value was only happen when vfork process change oom_adj. but vfork()ed process call exec() soon. userland monitor program don't confuse.
Plus, if you can post any troublesome testcase, I can fix it. this is not essential code in this patch.
> > @@ -1046,12 +1046,13 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf, > > put_task_struct(task); > > return -EINVAL; > > } > > - if (oom_adjust < task->mm->oom_adj && !capable(CAP_SYS_RESOURCE)) { > > + if (oom_adjust < task->signal->oom_adj && !capable(CAP_SYS_RESOURCE)) { > > task_unlock(task); > > put_task_struct(task); > > return -EACCES; > > } > > - task->mm->oom_adj = oom_adjust; > > + task->signal->oom_adj = oom_adjust; > > + task->mm->oom_adj_cached = OOM_CACHE_DEFAULT; > > task_unlock(task); > > put_task_struct(task); > > if (end - buffer == 0) > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > > index 7acc843..f93f97f 100644 > > --- a/include/linux/mm_types.h > > +++ b/include/linux/mm_types.h > > @@ -240,7 +240,8 @@ struct mm_struct { > > > > unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */ > > > > - s8 oom_adj; /* OOM kill score adjustment (bit shift) */ > > + s8 oom_adj_cached; /* mirror from signal_struct->oom_adj. > > + in vfork case, multiple processes use the same mm. */ > > > > cpumask_t cpu_vm_mask; > > > > diff --git a/include/linux/oom.h b/include/linux/oom.h > > index a7979ba..a219480 100644 > > --- a/include/linux/oom.h > > +++ b/include/linux/oom.h > > @@ -3,6 +3,7 @@ > > > > /* /proc/<pid>/oom_adj set to -17 protects from the oom-killer */ > > #define OOM_DISABLE (-17) > > +#define OOM_CACHE_DEFAULT (15) > > /* inclusive */ > > #define OOM_ADJUST_MIN (-16) > > #define OOM_ADJUST_MAX 15 > > diff --git a/include/linux/sched.h b/include/linux/sched.h > > index 3ab08e4..e10b12b 100644 > > --- a/include/linux/sched.h > > +++ b/include/linux/sched.h > > @@ -629,6 +629,8 @@ struct signal_struct { > > unsigned audit_tty; > > struct tty_audit_buf *tty_audit_buf; > > #endif > > + > > + s8 oom_adj; /* OOM kill score adjustment (bit shift) */ > > }; > > > > /* Context switch must be unlocked if interrupts are to be enabled */ > > I don't believe oom_adj is an appropriate use of signal_struct, sorry.
Real world and life aren't so simple... and linux too. At least, regression is definitely worst result. any other way is better than it.
> > > diff --git a/kernel/exit.c b/kernel/exit.c > > index 869dc22..c741a45 100644 > > --- a/kernel/exit.c > > +++ b/kernel/exit.c > > @@ -688,6 +689,7 @@ static void exit_mm(struct task_struct * tsk) > > enter_lazy_tlb(mm, current); > > /* We don't want this task to be frozen prematurely */ > > clear_freeze_flag(tsk); > > + mm->oom_adj_cached = OOM_CACHE_DEFAULT; > > task_unlock(tsk); > > mm_update_next_owner(mm); > > mmput(mm); > > This is similiar to an early proposal that wanted to keep an array of > oom_adj values for tasks attached to the mm in mm_struct. The problem is > that you're obviously losing information about all threads attached to the > mm any time one of the threads exits or writes to /proc/pid/oom_adj. That > information can only be regenerated with a tasklist scan.
I agree this. but I can't imazine this darkside. Can you please explain this? maybe, we can improve this implementaion obviously. reset at each thread exitting is caused by my lazy and small patch preference. a bit line adding can change this.
> > > diff --git a/kernel/fork.c b/kernel/fork.c > > index 9b42695..b7cb474 100644 > > --- a/kernel/fork.c > > +++ b/kernel/fork.c > > @@ -426,6 +427,7 @@ static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) > > init_rwsem(&mm->mmap_sem); > > INIT_LIST_HEAD(&mm->mmlist); > > mm->flags = (current->mm) ? current->mm->flags : default_dump_filter; > > + mm->oom_adj_cached = OOM_CACHE_DEFAULT; > > mm->core_state = NULL; > > mm->nr_ptes = 0; > > set_mm_counter(mm, file_rss, 0); > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > index 175a67a..eae2d78 100644 > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -58,7 +58,7 @@ unsigned long badness(struct task_struct *p, unsigned long uptime) > > unsigned long points, cpu_time, run_time; > > struct mm_struct *mm; > > struct task_struct *child; > > - int oom_adj; > > + s8 oom_adj; > > > > task_lock(p); > > mm = p->mm; > > @@ -66,7 +66,10 @@ unsigned long badness(struct task_struct *p, unsigned long uptime) > > task_unlock(p); > > return 0; > > } > > - oom_adj = mm->oom_adj; > > + > > + if (mm->oom_adj_cached < p->signal->oom_adj) > > + mm->oom_adj_cached = p->signal->oom_adj; > > This conditional will never be true since mm->oom_adj_cached is > initialized to 15, which is the upper bound on which p->signal->oom_adj > may ever be, so mm->oom_adj_cached never gets changed from > OOM_CACHE_DEFAULT.
Ah, good catch. this condition shold be reserve. thanks.
> Thus, this patch doesn't even work, and you probably would have noticed > that if you'd checked /proc/pid/oom_score for any pid. > > Even if mm->oom_adj_cached _was_ properly updated here, > /proc/pid/oom_score would be out of sync with more negative oom_adj values > for threads sharing the mm_struct since it calls badness() for only a > single thread.
Hm, I don't think this is serious problem. but I can fix it easily because badness() isn't fast-path.
> > + oom_adj = mm->oom_adj_cached; > > if (oom_adj == OOM_DISABLE) { > > task_unlock(p); > > return 0; > > @@ -350,7 +354,7 @@ static int oom_kill_task(struct task_struct *p) > > > > task_lock(p); > > mm = p->mm; > > - if (!mm || mm->oom_adj == OOM_DISABLE) { > > + if (!mm || p->signal->oom_adj == OOM_DISABLE) { > > task_unlock(p); > > return 1; > > }
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