On 22/05/19 17:04, Marcelo Tosatti wrote: > Consider sequence of wakeup events as follows: > 20us, 200us, 20us, 200us... I agree it can happen, which is why the grow/shrink behavior can be disabled for halt_poll_ns. Is there a real-world usecase with a sequence like this? The main qualm I have with guest-side polling is that it encourages the guest admin to be "impolite". But I guess it was possible even now to boot guests with idle=poll, which would be way more impolite... Paolo > If one enables guest halt polling in the first place, > then the energy/performance tradeoff is bend towards > performance, and such misses are harmful. > > So going to add something along the lines of: > > "If, after 50 consecutive times, block_time is much larger than > halt_poll_ns, then set cpu->halt_poll_ns to zero". > > Restore user halt_poll_ns value once one smaller block_time > is observed. > > This should cover the full idle case, and cause minimal > harm to performance. > > Is that OK or is there any other characteristic of > adaptive halt poll you are looking for?
