Re: [patch v2 1/2] oom: avoid killing a task if a thread sharing its mm cannot be killed

[David Rientjes <rientjes@google.com>]

On Wed, 18 Aug 2010, KAMEZAWA Hiroyuki wrote:

> > Is it worth adding
> > 
> > 	if (unlikely(current->signal->oom_score_adj == OOM_SCORE_ADJ_MIN))
> > 		atomic_dec(&current->mm->oom_disable_count);
> > 
> > to exit_mm() under task_lock() to avoid the O(n^2) select_bad_process() on 
> > oom?  Or do you think that's too expensive?
> > 
> 
> Hmm, if this coutner is changed only under down_write(mmap_sem),
> simple 'int' counter is enough quick. 
> 

task->mm->oom_disable_count would be protected by task_lock(task) to pin 
the ->mm, which we already take in exit_mm() to set task->mm to NULL.  We 
can take task_lock() in the proc handler, oom killer, and exec() paths 
where we're interested in the accounting.

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