Intel hopes open-source effort will lower Linux power
LessWatts.org is a collection of tips and code Linux experts can use to cut power consumption.
Intel plans to launch an effort called LessWatts.org on Thursday, a combination of open-source software and helpful hints to reduce power consumption of Linux servers, PCs and gadgets.
LessWatts, to be detailed during a Intel Developer Forum speech by Renee James, vice president and general manager of Intel's Software and Solutions Group, is geared toward technically sophisticated folks from programmers to system administrators. It gathers together a number of Intel projects, such as the PowerTop utility for finding which software is pestering the processor and preventing it from dozing in low-power states.
Taking Intel's advice and fixes can trim about 10 watts of power consumption off a modern dual-processor server, said Dirk Hohndel, chief technologist of Intel open-source technology center. That's not a gargantuan amount--until you consider that if done correctly it's free power savings, that each watt of server energy saved cuts another 1.3 watts from air conditioning (according to Intel figures), and of course that 10 watts per server is a lot when multiplied by the thousands of servers that populate larger data centers.
Announcements of open-source contributions often carry an altruistic flavor, but don't believe for a minute that Intel is acting out of the goodness of its own heart. It would dearly love to make its server technology customers happier, and lower power consumption can help bring the chipmaker's vision of mobile Internet devices to fruition by extending battery life.
On a current laptop, running Fedora 7 from Red Hat uses about 21 watts. "If you apply six little changes we propose, that same laptop takes 15.5 watts," Hohndel said. "You have just added a more than an hour to your battery run time."
Intel is cooperating with various programmers and Linux sellers, so it's likely that some of its suggestions will be incorporated into standard software.
Pardon me while I nerd out here a bit, because I find this stuff intriguing. Here are some of the particulars of the work that Hohndel detailed:
"Race-to-idle" changes to the Linux scheduler, a component of the kernel that decides what the computer is concentrating on at any given moment. Processors actually consume less power if working in bursts of business followed by cooler, idler moments than if working at a constant pace, and scheduler changes can encourage this hurry-up-and-wait philosophy.
Compressed data in graphics-processor communications. The memory interface consumes power when transferring data from memory to the graphics chip, but it takes less if that data is compressed, and graphics chips have built-in abilities to decode that data. It takes power to decode--perhaps thousandths of a watt--but a half a watt can be saved in memory interface, Hohndel said.
Changes to higher-level software. One example: Linux has software to mix sounds such as system beeps and music useful on desktop machines, but that software often is installed on servers with basic sound chips that typically aren't used. And the sound mixer checks 50 times each second to see if somebody has fiddled with the volume control, prodding the processor into activity each time.
Dialing down network transfer rates. Dropping down from 1-gigabit-per-second Ethernet to a tenth that speed can save about 2 watts. "If you know when your link is needed and when it's idle, you can save power," Hohndel said.
The tickless Linux kernel This approach essentially trims out the processor busywork of checking for things to do regularly, instead letting it drift off into low-power states and then wake up when there's work to be done.