Date: Sun, 03 Jul 2005 01:03:08 -0000 From: Nate Lawson <nate@root.org> To: Colin Percival <cperciva@freebsd.org> Cc: acpi@freebsd.org, current@freebsd.org Subject: Re: New cpufreq framework and drivers Message-ID: <42013223.4080704@root.org> In-Reply-To: <42012739.9080501@freebsd.org> References: <41FFB53B.3020907@root.org> <42012739.9080501@freebsd.org>
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Colin Percival wrote: > Nate Lawson wrote: > >> Hardware drivers are of two types, absolute >> and relative. SpeedStep, Powernow, etc. are absolute drivers in that >> they set the cpu's base frequency. ACPI throttling, Longrun, etc. are >> relative drivers that reduce the processor's clock to a fraction of >> its current base (i.e., they have an additive effect.) > > > If my first glance at the patch is correct, this would have my laptop (a > 1.4GHz > Pentium M) reporting the availability of the frequencies 600MHz, 800MHz, > etc. > from enhanced speedstep, along with the frequencies 300MHz, 400MHz, > 500MHz, and > 700MHz obtained via 50% clock throttling. That is correct. The code to support relative drivers was removed before posting to give the basic framework more testing before I commit it shortly. The relative support will go in soon after that code is committed. There are a lot of nuances that you'll see when I post the relative states patch. For instance, if a state has the same frequency of another state, the one with the lower power consumption is preferred. > While this in itself is entirely valid, a clock speed of 700MHz obtained by > running the processor at 1400MHz with a 50% "duty cycle" would draw more > power > than a clock speed of 800MHz obtained by running the processor at 800MHz > with > a lower voltage; is there any mechanism to inform userland daemons of such > oddities? I would hate to see a daemon lowering the clock speed from > 800MHz > to 700MHz in an attempt to save power... If you look at the kernel interface (sys/sys/cpu.h, struct cf_setting), you'll see that frequency, power, latency, and other values are available. The user sysctl interface exports frequency/power values as follows: dev.cpu.0.freq=733 dev.cpu.0.freq_levels=1000/18200 733/15100 That is Mhz and mW, respectively. With synthetic states (ones derived from a base absolute frequency and a modifying relative frequency), the cpufreq framework builds a power estimate. For example, a level comprised of 1400 Mhz at 20000 mW and a 50% relative setting would have an exported power of 10000 mW since relative drivers give a linear reduction in power consumption. Your absolute setting of 800 Mhz would likely have a lower power level and so any daemon should take that into consideration. -- Nate _______________________________________________ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org"
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