[Samsung Galaxy Nexus] aron7awol:
First of all, the lmgtfy link is completely unnecessary. Why the attempt to insult my intelligence when I've done nothing but look at this issue objectively and come to conclusions based on math and real world data? You said, "I am referring to years and years of experience me and others have made for desktop PCs and laptops. Just google it." I asked what exactly I should Google since it wasn't obvious based on your obscure statement. I know perfectly well how to use Google, thanks.

Hey man, don't take any of this stuff personally. I commended you on the work you've done on your kernel. You created your own governor, Wheatley. Truly impressive stuff. I think you've managed to improve device responsiveness with the combination of Wheatley and C4, without a major hit on the battery. When the screen is on, responsiveness is the #1 priority. It's when the screen is off that I'm talking about here, because that's when efficiency is the name of the game.

So anyway, I followed the first two links from that Google search. The first link, the guy is discussing some hypothetical CPU that uses 24 W running at half speed and 34 W running at full speed. Well that's a CPU that is clearly more efficient running at full speed than half speed, since 34 < 24*2. Unfortunately, I don't know of any CPUs that work that way. If they did, why would they need lower speed steps at all? The second link was a glossary. I know what race to idle means. I understand the concept completely. It makes sense if and only if your CPU is more efficient at a higher frequency.

Now here we go. This is literally the first piece of evidence I have seen produced to potentially back up the race to idle theory with real data. Very interesting stuff. A few things do stick out to me, though:

1. The first test you did without the deep-idle state enabled is the result I would expect given everything I know about CPU power consumption thus far. The higher frequency is less efficient.

2. On the next test with the deep-idle state enabled, what's up with the battery percentage increasing at the beginning for the 1320 MHz test? Also, it appears that the 1320 MHz test started with 1% higher battery. If anything, it still appears that the higher frequency state is eating more battery, ignoring the percentage abnormalities. It looks like at best a wash.

Given the lack of current readings on Samsung devices, and the inherent inaccuracy of battery % display, I find it difficult to come to any real conclusions based on that data. However, it still doesn't really seem to support the race to idle theory. I see the higher frequency state eating more battery in both cases.

Don't get caught up on the equation representing power consumption perfectly. Nobody is claiming that. It does, however, seem to be a very good approximation. I showed that when I calculated the expected consumption ratio to be 6.99 and it turned out to be 6.80. It at least holds water, you have to admit that much.

Anyway, it's really easy enough to simplify this entire issue down to one thing: Is the CPU more efficient at a lower or higher frequency? Forget idle states, I'll pretend for this point of discussion that idle power consumption is zero. Race to idle still only makes sense if the higher frequency is more efficient. Period. And by efficient, I mean it uses less power to get the same amount of work done. I have seen zero evidence of any CPU where that is true, and produced a bunch of evidence to suggest the very opposite with the exact CPU we're talking about.

I've already produced data relevant to this discussion. This exact CPU was measured using almost 7 times as much power to run at a speed only 3.86 times faster. What else is there to see here? It is clearly much less efficient at the higher frequency. Therefore, racing to idle cannot possibly save power. It is literally impossible, no matter how awesome the idle state is. Unless, of course, there was a magic idle state that could actually charge the battery.

And for the record, you certainly have not explained to me why my estimates might be wrong. All you said was that I couldn't subtract 100% usage power consumption from idle consumption, and I never did that. This isn't about who's right and who's wrong. I started investigating this issue with a completely open mind; all I want to do is determine the best balance of performance when the screen is on and battery life when the screen is off. Everything I've seen so far has me absolutely convinced that lower frequencies are the way to go with the screen off.

Again, great work on your kernel. This is what the community is all about. Intelligent discussion and experimentation to figure out the best practices, and then everyone gets to reap the benefits.