On Fri, Mar 17, 2017 at 08:47:08AM +0100, Michal Hocko wrote: > On Thu 16-03-17 11:36:21, Tim Chen wrote: > [...] > > Perhaps we can only do this expedited exit only when there are idle cpus around. > > We can use the root sched domain's overload indicator for such a quick check. > > This is not so easy, I am afraid. Those CPUs might be idle for a good > reason (power saving etc.). You will never know by simply checking > one metric. This is why doing these optimistic parallelization > optimizations is far from trivial. This is not the first time somebody > wants to do this. People are trying to make THP migration faster > doing the similar thing. I guess we really need a help from the > scheduler to do this properly, though. I've been thinking about an API > (e.g. try_to_run_in_backgroun) which would evaluate all these nasty > details and either return with -EBUSY or kick the background thread to > accomplish the work if the system is reasonably idle. I am not really > sure whether such an API is viable though. > Peter, what do you think? Much pain lies this way. Also, -enocontext. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
