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? -- Michal Hocko SUSE Labs -- 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>
