On Tue, 24 May 2011, KOSAKI Motohiro wrote: > > > > This is unnecessary and just makes the oom killer egregiously long. We > > > > are already diagnosing problems here at Google where the oom killer > > > > holds > > > > tasklist_lock on the readside for far too long, causing other cpus > > > > waiting > > > > for a write_lock_irq(&tasklist_lock) to encounter issues when irqs are > > > > disabled and it is spinning. A second tasklist scan is simply a > > > > non-starter. > > > > > > > > [ This is also one of the reasons why we needed to introduce > > > > mm->oom_disable_count to prevent a second, expensive tasklist scan. > > > > ] > > > > > > You misunderstand the code. Both select_bad_process() and > > > oom_kill_process() > > > are under tasklist_lock(). IOW, no change lock holding time. > > > > > > > A second iteration through the tasklist in select_bad_process() will > > extend the time that tasklist_lock is held, which is what your patch does. > > It never happen usual case. Plz think when happen all process score = 1. > I don't care if it happens in the usual case or extremely rare case. It significantly increases the amount of time that tasklist_lock is held which causes writelock starvation on other cpus and causes issues, especially if the cpu being starved is updating the timer because it has irqs disabled, i.e. write_lock_irq(&tasklist_lock) usually in the clone or exit path. We can do better than that, and that's why I proposed my patch to CAI that increases the resolution of the scoring and makes the root process bonus proportional to the amount of used memory. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>