More progress on the Thinkpad T60 and Gentoo

[elfs]

Well, so far so good. I've enabled the CPU's auto-frequency governor, which reduces power usage quite a bit, as well as TICKLESS (turns off the kernel's internal heartbeat) and USB suspend (turns off USB connectors when not in use), and so far it still suspsends to RAM nicely. According to Intel's powertop program, I'm saving over a Watt of power, which will increase my battery life some 8% or so. Not too shabby.

I've chosen the name Chi. It's short and easy to type, and just because I wanted to. Kurumi was my second choice.

This morning, I accidentally issued the wrong command to the laptop: instead of suspend, I sent it hibernate, which does not just suspend all operations yet keeps the system "live" in memory, but actually writes out that live image to disk and shuts everything down completely and powers off. To my pleasure, the system came back to life without a hitch when I got into work: the OS booted, saw that there was a pending image, and loaded it. It worked great.

And according to Intel's powertop program, I have about 4.5 hours of battery life if all I'm doing is word processing. Now that's good news. I can take it to the cafe' with me without having to lug the cord.

Comments

[woggie.livejournal.com]

Wait. What effects does tickless have? Is it like speeding up the hardware, or what? Doesn't that mess up the clock?

[elfs.livejournal.com]

No, it's the other way around: it slows down the hardware. There's a setting in the kernel for how fast do you want it to check the "work to do" queue: once every millisecond, once every 4 milliseconds, once every 10 milliseconds. are the most common settings. But what if there's no work to be done in the next 30 milliseconds? Even at the slowest setting, once every ten milliseconds, that means the kernel wakes up the CPU to examine the queue twice before anything meaningful happens.

The Tickless kernel uses a specialized low-power clock found in modern CPU architectures and associates its work queue with that clock. Work queues are always time-sensitive, so it's no hardship to put the CPU to sleep for as long as possible, then wake it up as needed. Hardware-driven events can always be inserted and generate "wake up now." This saves energy by delaying as long as possible the next wake/work/sleep cycle of the CPU for actual work cycles. If all I'm doing is word processing, that's a big win.

[ewhac.livejournal.com]

"Hibernate" has long been the most reliable way to suspend your session and put the laptop to sleep. This is because, on wakeup, the BIOS gets a chance to initialize everything before handing control back to Linux. On hardware where the manufacturer(s) have unconscionably refused to provide documentation, this is often the only way to get any kind of suspend at all.

ThinkPads are among the best supported laptops under Linux. I presume you've found ThinkWiki (http://thinkwiki.org/)?