Unit Four                   CSCI523                 Operating Systems

Lecture

 1)Explain the rationale behind ioctl and its associated services.
   a)Ioctl provides a way the user can change the behavior of a
     device driver by setting or clearing flags in kernel data
     structure that is checked by the driver when its activated.
   b)Sockopt provides similar services for changing the behavior
     of the network protocol stack.
   c)Fctl switches synchronous I/O calls to asynchronous calls.
   d)Linux /proc files can replace all of these kernel services.
 2)Desribe the general format of an ioctl call.
   ioctl(fd, command, p1, p2, ...)
   fd - opened raw device in /dev/ (link to device driver)
   command - get or set bit, bit pattern, or data structure
   p1 - pointer to user's local copy
   p2 - optional arguments...


Linux Kernel Development, 2nd ed. - Robert Love
Chapter Ten - Timers and Time Management
 1)List the seven step timer algorithm from most urgent to least
   urgent responsibility. p. 158
   a)Increment the jiffy count
   b)If one second elapsed, update time-of-day
   c)Check SMP task queues and reshuffle if unbalanced
   d)Reschedule current task if timeslice expried
   e)Check for timeouts and execute callbacks
   f)Update user vs system time
   g)Update profiling if enabled for this task
 2)Describe the system behavior of one second interval timer
   interrupt versus a one micro second interval timer interrupt
   on:
   a)user level interval resolution
   b)select() system service
   c)task sheduling latency resolution
   d)the audio driver
   e)precent of system overhead or relative time spent in kernel
   Support or refute the switch in Linux from a timer interval
   of 10 milliseconds to 1 millisecond. p. 158-161
 3)The Pentium series has a microsecond time stamp counter (TSC)
   register.  Explain how to use this register to construct a
   tickless OS.  (hint: rename the register to "jiffies_64.")
    p. 162-164
 4)Describe the problem and solution to using a 1 millisecond
   timer interval with a 32-bit jiffy counter. p. 164-165
 5)Contrast the RTC, PIT, APIC, and TSC. p. 166-167