On Tue, 13 Apr 2010 17:08:18 -0700 Salman <sqazi@xxxxxxxxxx> wrote: > As we discussed earlier this year, Google has an implementation that > it would like to share. I have finally gotten around to porting it to > v2.6.33 and cleaning up the interfaces. It is provided in the > following messages for your review. I realize that when we first > discussed this idea, a lot of ideas were presented for enhancing it. > Thanks alot for your suggestions. I haven't gotten around to > implementing any of them. again I'll chime in to support this effort; it's the right thing to do for power limiting (as opposed to taking cores offline), and I'm happy to see progress being made. I'll start playing with your patches and use timechart to see how well it works, including to see how well things align... > The ones that I still find appealing are: > > 0. Providing approximate synchronization between cores, regardless > of their independant settings in order to improve power savings. We > have to balance this with eager injection (i.e. avoiding injection > when an interactive task needs to run). I still would like to see this ;-) It's a *HUGE* instant power delta. But it does not have to be perfect. As long as "on average" we align we're good enough. the easiest way is to round the time of the start of idle injection up to, say, double the duration of the injection period... and maybe to whole seconds or some round value of jiffies as well. It could even be done by "creeping" towards an aligned situation... rather than forcing instant alignment, as long as each time we inject idle time we get a step closer to being aligned.. very soon we WILL be aligned. (for example, if a cpu notices it's on the late side of an alignment window, it could inject a little shorter than usual, while if it notices it's a little early, it can inject a little longer) > A stricter synchronization between cores is needed to make idle cycle > injector work on hyperthreaded systems. This is a some what separate > issue, as there should only be one idle cycle injector minimum idle > setting per physical core. actually... while the HT case is clearly required to be solved to get actual power limits, ideally we can solve it using the same tricks we use for the above, just with a stronger bias... I don't think we need to force the admin to set the same value per se, it's something that's just a matter of having the policy guy do this right... (but if you want to do "effective injection %age is minimum of the two" or so, I can live with that) > -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
