Linux captures the 'green' flag, beats Windows 2008 power-saving measures (Network World)

from the article: "A tickless version of the Linux kernel now reportedly exists that
interrupts the CPU less frequently, but was not part of the Linux distribution kernels we
tested — although that addition is planned in future editions of Red Hat and SUSE."

it not only "reportedly exists", but gives me significant power savings on my Ubuntu Hardy
laptop.. it sounds like Red Hat (Enterprise, not Fedora!) and SUSE could do with catching up a
kernel rev or two.. 2.6.21 was the first version with it I believe.

good to hear that Linux is better than Windows 2008 even without tickless though.. there are
some serious improvements coming for RHEL/SUSE!

This isn't a particularly well-conducted test.

Most notably:

- They measure power draw under load without measuring performance. A configuration that
simply went slower and required more power in total (due to greater time requirements) to
complete a task would thus "win" their test.

- They used the "power saver" instead of "balanced" profile for 2008 server, which is a poor
choice for a server under any circumstances and may even use *more* power to complete a given
job because it can prevent the CPU from spiking to max performance to finish a job quickly.

- Their "load" test was scripted email generation not something actually likely to make a
modern server work like a file or database server load generator. I guess if it was
virus-scanning and spam-checking vast piles of mail...

- They don't seem to know that CPUs, including server CPUs, supported the HLT instruction for
reduced CPU power draw well before frequency and voltage stepping arrived on the scene even
for laptops. Servers haven't run on full-tilt power max when idle for a *long* time, but they
seem to think they do.

- They fall for the all-too-common pretty but misleading non-zero-y-origin graph trap.

- Their results aren't really very significant anyway. Given their poor methodology I'd say
they're close to useless.

A more useful test would've defined jobs to do (100 loops of this database load test; process
1 million spam-filtered and virus-scanned emails; etc). It would measure total energy (joules)
consumed to complete the task in various power modes. It would then ALSO consider idle draw
and full-tilt peak draw - both of which matter for, among other things, cooling needs - as
secondary concerns.

That said, with virtualized servers becoming more popular and most VM environments crippling
power management peak draw is certainly a concern when evaluating the hardware (if not the
OS).

Shorter Network World: We have no idea what we're talking about!

All data is useful, including this report from network world. Looking forward to the stats
from the tickless kernel though.