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This is proving stable and<br />> > > effective on virtually all uniprocessor machines and will benefit<br />> > > systems that desire power savings. SMP kernels (even on UP machines)<br />> > > still misbehave so this config option is not available by default for<br />> > > this stable kernel.<br />> ><br />> > I've been curious for some time if this would actually show any<br />> > measurable power savings. So I hooked up my laptop to a gizmo[1] that<br />> > shows how much power is being sucked.<br />> ><br />> > both before, and after, it shows my laptop when idle is pulling 21W.<br />> > So either the savings here are <1W (My device can't measure more<br />> > accurately than a single watt), or this isn't actually buying us<br />> > anything at all, or something needs tuning.<br />><br />> Ah interesting. It needs to be totally idle for a period of time before<br />> anything starts to happen at all. After about a minute of doing nothing,<br />> it started to fluctuate once a second 20,21,19,20,19,20,18,21,19,20,22<br />> etc..<br />><br />> Goes no lower than 18W, and only occasionally peaks above the old idle<br />> power usage. Not bad at all.<br />><br />> Causing any activity at all puts it back to the 'have to wait a while<br />> for things to start happening' state again.<br /><br />Thanks for testing it. Indeed skipping the ticks alone does not really save <br />any significant amount of power. The real chance for power savings comes from <br />using this period for smarter C state programming. The other thing as you've <br />noticed is that timers need to be curbed or minimised to get the maximum <br />benefit and the ondemand governor alone, which unfortunately shows up as <br />something not obvious in timertop, polls at 140HZ itself - fiddling with <br />ondemand/ settings in sys can drop this but slows the rate at which it <br />adapts.<br /><br />I've basically stopped doing any development on dynticks at this time because <br />I simply do not know enough about the interaction between the IO Apic and <br />what is happening on SMP. The code to handle SMP seems sane, but I'll need <br />outside help to cope with whatever the IO APIC is doing. UP is working fine, <br />but it won't be long before truckloads of SMP laptops are here.<br /><br />Cheers,<br />Con<br />-<br />To unsubscribe from this list: send the line "unsubscribe linux-kernel" in<br />the body of a message to majordomo@vger.kernel.org<br />More majordomo info at <a href="http://vger.kernel.org/majordomo-info.html">http://vger.kernel.org/majordomo-info.html</a><br />Please read the FAQ at <a href="http://www.tux.org/lkml/">http://www.tux.org/lkml/</a><br /><br /></pre></td><td width="32" rowspan="2" class="c" valign="top"><img src="/images/icornerr.gif" width="32" height="32" alt="\" /></td></tr><tr><td align="right" valign="bottom"> 聽 </td></tr><tr><td align="right" valign="bottom">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerl.gif" width="32" height="32" alt="\" /></td><td class="c">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerr.gif" width="32" height="32" alt="/" /></td></tr><tr><td align="right" valign="top" colspan="2"> 聽 </td><td class="lm">Last update: 2006-01-05 00:14 聽聽 [from the cache]<br />漏2003-2020 <a href="http://blog.jasper.es/"><span itemprop="editor">Jasper Spaans</span></a>|hosted at <a href="https://www.digitalocean.com/?refcode=9a8e99d24cf9">Digital Ocean</a> and my Meterkast|<a href="http://blog.jasper.es/categories.html#lkml-ref">Read the blog</a></td><td>聽</td></tr></table><script language="javascript" src="/js/styleswitcher.js" type="text/javascript"></script></body></html>