On Wed, 9 Sep 2009, Robert Noland wrote: > On Wed, 2009-09-09 at 10:20 +0930, Daniel O'Connor wrote: > > On Wed, 9 Sep 2009, Ian Smith wrote: > > > > > Does anyone know if it is possible to determine if this is > > > > > the case? ie is there a way to be informed if throttling has > > > > > occurred? > > > > > > Might be easier to hack powerd.c as an existing pretty > > > lightweight way of monitoring CPU freq (to log or signal on > > > detected freq lowered by throttling, say?) even if you don't > > > need/want it to actually vary freq according to load, eg setting > > > idle/busy shift factors to 'never/always'? > > > > Hmm, that could work. > > > > It seems odd to me that there is no direct way the BIOS can notify > > the OS it's throttling the CPU though. > > Some BIOS can and do send an ACPI event when the proc gets hot. In > my experience, this was not a good thing though. The BIOS that I > remember dealing with this on would continuously send the alarms, so > while TCC would kick in and throttle the CPU, the event processing > kept it at 100% utilization until it was powered off to cool. I have
Ugh! This system seems to stall for a few seconds and then come back, I haven't see any messages about it in dmesg though. > also been able to determine that TCC had kicked in by looking at the > cpu frequency via sysctl and comparing that to the max frequency > reported for the proc. Yeah, although I couldn't run ps when the CPU was stalled so I'm not sure if I'd catch it or not :) > If the BIOS sent the alarm, but throttled the rate it wouldn't have > been so bad. Not that I had any active fan control on that box to do > anything about it really, but TCC might have actually worked if it > wasn't flooding the acpi event processor. Having the BIOS or CPU do it automatically is sensible since it's a time critical task.. Some basic notification would be nice though. It boggles my mind how difficult it is to do such basic things sometimes.. -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
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