How can I find out if CPU throttling is enabled?
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From: David Kirkby on 24 Jul 2010 00:12 Is there any way from a command line that I can determine if a system has some sort of power control which will reduce the CPU speed when the system is idle? I know I could look at /etc/power.conf, but I want to do this from a script and get a simple yes/no answer. Parsing files like /etc/power.conf is not so easy, as there are various way of specifying CPU power modes.
From: Stefan Krueger on 24 Jul 2010 08:02 On 2010-07-24, David Kirkby <drkirkby(a)gmail.com> wrote: > Is there any way from a command line that I can determine if a system > has some sort of power control which will reduce the CPU speed when > the system is idle? I know I could look at /etc/power.conf, but I want > to do this from a script and get a simple yes/no answer. Parsing files > like /etc/power.conf is not so easy, as there are various way of > specifying CPU power modes. IIRC you can use kstat to check for that, e.g. kstat -m cpu_info -i 0 -s supported_frequencies_Hz See http://blogs.sun.com/mhaywood/entry/powernow_for_solaris Keep in mind that frequency changing on older dual core AMDs is not supported (i.e. below family 16 or 0x10 HTH
From: Andrew Gabriel on 24 Jul 2010 12:27 In article <8b0324Ft5nU1(a)mid.uni-berlin.de>, Stefan Krueger <stadtkind2(a)gmx.de> writes: > On 2010-07-24, David Kirkby <drkirkby(a)gmail.com> wrote: >> Is there any way from a command line that I can determine if a system >> has some sort of power control which will reduce the CPU speed when >> the system is idle? I know I could look at /etc/power.conf, but I want >> to do this from a script and get a simple yes/no answer. Parsing files >> like /etc/power.conf is not so easy, as there are various way of >> specifying CPU power modes. > > IIRC you can use kstat to check for that, e.g. > > kstat -m cpu_info -i 0 -s supported_frequencies_Hz > > See http://blogs.sun.com/mhaywood/entry/powernow_for_solaris > > Keep in mind that frequency changing on older dual core AMDs is not > supported (i.e. below family 16 or 0x10 Also, on Nehalem, Solaris's power-aware dispatcher will power down cores if there aren't enough threads to keep them all busy. This will usually result in extra thermal headroom for the cores which are still running, and the chip will automatically overclock them, depending on the amount of extra thermal headroom available (Intel Turboboost). If you don't want the clockspeed to vary according to available thermal headroom, you would have to disable Turboboost in the BIOS. -- Andrew Gabriel [email address is not usable -- followup in the newsgroup]
From: Dr. David Kirkby on 24 Jul 2010 16:17 On Jul 24, 1:02 pm, Stefan Krueger <stadtki...(a)gmx.de> wrote: > On 2010-07-24, David Kirkby <drkir...(a)gmail.com> wrote: > > > Is there any way from a command line that I can determine if a system > > has some sort of power control which will reduce the CPU speed when > > the system is idle? I know I could look at /etc/power.conf, but I want > > to do this from a script and get a simple yes/no answer. Parsing files > > like /etc/power.conf is not so easy, as there are various way of > > specifying CPU power modes. > > IIRC you can use kstat to check for that, e.g. > > kstat -m cpu_info -i 0 -s supported_frequencies_Hz > > Seehttp://blogs.sun.com/mhaywood/entry/powernow_for_solaris > > Keep in mind that frequency changing on older dual core AMDs is not > supported (i.e. below family 16 or 0x10 > > HTH That only tells me if the chip supports multiple frequencies - not whether this is feature is enabled in software and/or BIOS. It's potentially a problem building some software which does time comparisons if the clock frequency changes. In particular, I have ATLAS http://math-atlas.sourceforge.net/ dave
From: Dr. David Kirkby on 24 Jul 2010 16:31
On Jul 24, 5:27 pm, and...(a)cucumber.demon.co.uk (Andrew Gabriel) wrote: > In article <8b0324Ft5...(a)mid.uni-berlin.de>, > Stefan Krueger <stadtki...(a)gmx.de> writes: > > > > > On 2010-07-24, David Kirkby <drkir...(a)gmail.com> wrote: > >> Is there any way from a command line that I can determine if a system > >> has some sort of power control which will reduce the CPU speed when > >> the system is idle? I know I could look at /etc/power.conf, but I want > >> to do this from a script and get a simple yes/no answer. Parsing files > >> like /etc/power.conf is not so easy, as there are various way of > >> specifying CPU power modes. > > > IIRC you can use kstat to check for that, e.g. > > > kstat -m cpu_info -i 0 -s supported_frequencies_Hz > > > Seehttp://blogs.sun.com/mhaywood/entry/powernow_for_solaris > > > Keep in mind that frequency changing on older dual core AMDs is not > > supported (i.e. below family 16 or 0x10 > > Also, on Nehalem, Solaris's power-aware dispatcher will power down > cores if there aren't enough threads to keep them all busy. This > will usually result in extra thermal headroom for the cores which > are still running, and the chip will automatically overclock them, > depending on the amount of extra thermal headroom available > (Intel Turboboost). If you don't want the clockspeed to vary > according to available thermal headroom, you would have to disable > Turboboost in the BIOS. > > -- > Andrew Gabriel > [email address is not usable -- followup in the newsgroup] Do any SPARC processors support any sort of CPU throttling? The most modern SPARC I have access to, a T5240, shows no sign of this: kirkby(a)t2:[~] $ kstat -m cpu_info -i 0 -s supported_frequencies_Hz module: cpu_info instance: 0 name: cpu_info0 class: misc supported_frequencies_Hz 1166666144 It basically looks like I'm stuffed in any attempt to find out if someone's computer has any sort of CPU throttling enabled or not. I know ATLAS http://math-atlas.sourceforge.net/ tries to determine this, but I'm not sure what method it uses. I think I'm right in saying ATLAS will refuse to build if CPU throttling enabled, unless one passes an option to the configure script. I know 'powertop' will often show the CPU speed over 3334 MHz on my Ultra 27, despite the fact the highest supported frequency is 3334 MHz. I can't quite see the point in having 3333 MHz and 3334 MHz, but that's what appears to be supported. drkirkby(a)hawk:~$ kstat -m cpu_info -i 0 -s supported_frequencies_Hz module: cpu_info instance: 0 name: cpu_info0 class: misc supported_frequencies_Hz 1600000000:1733000000:1867000000:2000000000:2133000000:2267000000:2400000000:2533000000:2667000000:2800000000:2933000000:3067000000:3200000000:3333000000:3334000000 drkirkby(a)hawk:~$ That's no doubt when the machine has enough thermal headroom to run faster. Dave |