Re: [Cooker] why does kapm-idled spin the cpu so often?

[Paul Giordano]

I think you're confusing "charged to" with "using" - read the paragraph a bit more carefully. The kernel has a facility to call the BIOS IDLE function with APM enabled when nothing else is happening - while in that BIOS call CPU "ownership" is the kapm-idled task, and the time increments accordingly. In reality, since the actual execution is in the BIOS IDLE routine, no CPU consumption is occurring - the BIOS should be putting your machine into a sleep state (If your BIOS is configured appropriately.) Basically APM (and ACPI, for that matter) uses the systems' BIOS as the arbiter and executor of power savings - rather than the kernel doing it directly. Hope this helps... Gio ----- Original Message ----- From: "Bruce F. Press" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Sunday, April 15, 2001 7:52 AM Subject: Re: [Cooker] why does kapm-idled spin the cpu so often? > Yes, yes, we've heard this before.  It is not a satisfactory answer, > clearly the "idle" loop in kapm-idled could use a nice sleep(15) or > something!! > > > Chmouel Boudjnah wrote: > > > > SI Reasoning <[EMAIL PROTECTED]> writes: > > > > > There are good stretches of the day where my CPU spins > > > at around 50% or more and the process spinning is > > > kapm-idled. This is not a problem in 7.2. > > > > --=-=-= > > http://www.tux.org/lkml/#s14-1: > > > > 1.Why is kapmd using so much CPU time? > >         (REG) Don't worry, it's not stealing valuable CPU time from > >         other processes. It's just consuming idle cycles (normally > >         charged to the idle task, which is displayed differently in > >         top).  Normally, when your system is idle, the system idle > >         task is run, and this is shown as idle time (i.e. the "unused" > >         CPU time is not charged to a specific process). With APM > >         (Advanced Power Management), a special idle task (kapmd) is > >         required so that greater power saving techniques can be > >         enabled. So now, the "unused" CPU time is charged to the kapmd > >         task instead. > > > > --=-=-= > > > > --=-=-= > > http://olstrans.sourceforge.net/release/OLS2000-apm/OLS2000-apm.html: > > > > In 2.2 and before, we basically had a hook into the idle loop, so that > > if we had APM enabled, we would just tell the BIOS that we're > > idle. In 2.3, Linus thought it would be a good idea if we had a > > separate power management idle loop, so (he) we invented the > > kernel APM daemon and I started getting bug reports about this > > process that was using all our time, called kapmd. And if you sat > > there just running top on a 2.3 kernel, the top process, if you're > > not doing anything else, will be kapmd and it will be using like > > 85% or 90% or 95% of your CPU time. These people were worried > > because it was idle: why is it using all of the time? Well > > actually, it's just that the time is getting accounted to that > > process. It's not doing anything, it's the idle loop. [26m, 12s] > > --=-=-= > > > > -- > > MandrakeSoft Inc                     http://www.chmouel.org > >                       --Chmouel