Messages in this thread | | | Date | Thu, 11 Sep 2014 13:31:13 +0530 | From | Chintan Pandya <> | Subject | Re: [PATCH v4 2/2] ksm: provide support to use deferrable timers for scanner thread |
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I don't mean to divert the thread too much. But just one suggestion offered by Harshad.
Why can't we stop invoking more of a KSM scanner thread when we are saturating from savings ? But again, to check whether savings are saturated or not, we may still want to rely upon timers and we have to wake the CPUs up from IDLE state.
>> here. Can't we create a new (timer) infrastructure that does the right >> thing? Surely this isn't the only such case. > > A sleep-walking timer, that goes to sleep in one bed, but may wake in > another; and defers while beds are empty? I'd be happy to try using > that for KSM if it already existed, and no doubt Chintan would too
This is interesting for sure :)
> > But I don't think KSM presents a very good case for developing it. > I think KSM's use of a sleep_millisecs timer is really just an apology > for the amount of often wasted work that it does, and dates from before > we niced it down 5. I prefer the idea of a KSM which waits on activity > amongst the restricted set of tasks it is tracking: as this patch tries. > > But my preference may be naive: doing lots of unnecessary work doesn't > matter as much as waking cpus from deep sleep.
This is exactly the preference we are looking for. But yes, cannot be generalized for all.
> >> >> I know both RCU and some NOHZ_FULL muck already track when the system is >> completely idle. This is yet another case of that. > > Hugh
-- Chintan Pandya
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