Annotation of wikisrc/projects/project/tickless.mdwn, revision 1.2

1.1       riastrad    1: [[!template id=project
                      2: 
                      3: title="Tickless NetBSD with high-resolution timers"
                      4: 
                      5: contact="""
                      6: [tech-kern](mailto:tech-kern@NetBSD.org)
                      7: """
                      8: 
                      9: mentors="""
                     10: [Taylor R Campbell](mailto:riastradh@NetBSD.org)
                     11: """
                     12: 
                     13: category="kernel"
                     14: difficulty="hard"
                     15: duration="2-3 months"
                     16: 
                     17: description="""
                     18: NetBSD configures a timer device to deliver a periodic timer interrupt,
                     19:  usually every 10 ms, in order to count time, wake threads that are
                     20:  sleeping, etc.
                     21: This made sense when timer devices were expensive to program and CPUs
                     22:  ran at MHz.
                     23: But today, CPUs run at GHz; timers on modern x86, arm, mips,
1.2     ! riastrad   24:  etc. hardware are cheap to reprogram; programs expect greater than
1.1       riastrad   25:  10 ms resolution for sleep times; and mandatory periodic activity on
                     26:  idle machines wastes power.
                     27: 
                     28: There are three main miletones to this project:
                     29: 
                     30: 1. Design a machine-independent high-resolution timer API, implement it
                     31:  on a couple machines, and develop tests to confirm that it works, in
                     32:  order to enable high-resolution sleeps.
                     33: 
                     34: 2. Convert all the functions of the periodic 10 ms timer, `hardclock',
                     35:  to schedule activity only when needed.
                     36: 
                     37: 3. Convert the various software subsystems that rely on periodic timer
                     38:  interrupts every tick, or every second, via
                     39:  [callouts](http://netbsd.gw.com/cgi-bin/man-cgi?callout++NetBSD-current),
                     40:  either to avoid periodic work altogether, or to batch it up only when
                     41:  the machine is about to go idle, in order to reduce the number of
                     42:  wakeups and thereby reduce power consumption.
                     43: """
                     44: ]]
                     45: 
                     46: [[!tag gsoc]]

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