| Weekly edition | Kernel | Security | Distributions | Search |
| Archives | Calendar | Subscribe | Write for LWN | LWN.net FAQ |
The dynamic tick patch
The dynamic tick patch
Posted Jun 9, 2005 15:53 UTC (Thu) by jg (subscriber, #17537)Parent article: The dynamic tick patch
It turns out to take a lot of power to power up a CPU chip. It is much more than just the raw number of instructions that might execute.
So taking a 1000hz clock interrupt actually consumes a significant amount of power.
I don't know what the stats are for x86 in this area is though.
As an aside, other things take lots more power than you might naively expect. On StrongARM's of, say 3 years ago, the cost of a miss in cache to reference main memory was equivalent to executing of order a hundred
instructions in cache.
(Log in to post comments)
The dynamic tick patch
Posted Jun 16, 2005 9:33 UTC (Thu) by farnz (subscriber, #17727) [Link]
Also, most CPUs take a long time to switch from run to sleep; at 1kHz tick, there's a good chance that the "sleeping" CPU is actually running for a decent stretch of time. As they can switch back almost instantly, a good power saving technique is to try and maximise the time between a "go to sleep" command, and the next wakeup, which is exactly what dynamic ticks does.