Messages in this thread | | | Date | Tue, 14 Oct 2003 17:12:27 -0700 | From | Andrew Morton <> | Subject | Re: OK to set PF_MEMDIE on cleanup tasks? |
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"Paul E. McKenney" <paulmck@us.ibm.com> wrote: > > Hello! > > We have tasks that actively return memory to the system, which we > would like to exempt from the OOM killer, as killing such tasks under > low-memory conditions would indeed be counterproductive. It looks like > the "official" way to do this is to catch/ignore signal 15, which results > in PF_MEMDIE being set (in the 2.6 kernel), thus preventing the OOM killer > from killing the task again. I don't see where PF_MEMDIE is cleared, > though there are a number of subtle ways one might do this that I would > have missed.
The PF_MEMDIE flag is there so the oom killer doesn't just sit there hitting the same task over and over again.
We leave PF_MEMDIE set because we expect the task to exit, or to not want any more oomkiller attention.
The SIGTERM behaviour is there because the CAP_SYS_RAWIO process may need to release critical resources.
So as long as your process has CAP_SYS_RAWIO, everything happens to work as you want it. I don't think it was really designed that way though.
> So... Is it considered legit to simply set PF_MEMDIE when creating > the cleanup task? Or is there some reason that one should deal with > signal 15?
Well it's all very unconventional. Catching SIGTERM seems like a suitable way to do what you want to do.
Possibly your special process should also run as PF_MEMALLOC. I've seen that done before, with success. There is no existing API with which this can be set.
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