On Sunday 17 February 2008 04:58:52 am Andriy Gapon wrote: > Come on, guys, simple yes or no would be enough for me :-) > > on 14/02/2008 22:31 Andriy Gapon said the following: > > Dear hackers, > > I'd like to check with you if my understanding of some code is correct. > > > > If we speak about a typical older i386 system, with UP and "AT" PIC, I > > think this is how the CPU utilization stats are collected. > > RTC is configured to generate interrupts (IRQ8) 128 times per second. > > Each time interrupt is generated RTC interrupt handler (I will use > > simple non technical terms) takes a peek at what was interrupted and > > depending on the properties of that thing (kernel thread) bills a tick > > to particular category. E.g. if it sees that the "idle" thread is > > interrupted then a tick is billed to "idle", if an interrupt thread is > > interrupted (software or hardware) then a tick is billed to interrupt, > > if a thread is running user-mode code then a tick is billed to "user" or > > "nice", otherwise it's "system". > > I understand that I oversimplify, but is the above correct in general ? > > > > Another, unrelated, question. > > Considering this snippet from sys/i386/isa/atpic.c, i8259_init(): > > #ifndef PC98 > > /* OCW2_L1 sets priority order to 3-7, 0-2 (com2 first). */ > > if (!slave) > > outb(pic->at_ioaddr, OCW2_R | OCW2_SL | OCW2_L1); > > #endif > > > > Do I understand correctly the code and the comment that here we use a > > feature of 8259 PIC that can be called "cyclic shift of interrupt > > priorities" ? > > So, we really have the following order of interrupts, from higher > > priority to lower: 3-7,0,1,8-15? Considering two chained 8259s, of > > course.
Yes and yes. -- John Baldwin _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
