The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kernel/Kconfig.hz

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    1 #
    2 # Timer Interrupt Frequency Configuration
    3 #
    4 
    5 choice
    6         prompt "Timer frequency"
    7         default HZ_250
    8         help
    9          Allows the configuration of the timer frequency. It is customary
   10          to have the timer interrupt run at 1000 Hz but 100 Hz may be more
   11          beneficial for servers and NUMA systems that do not need to have
   12          a fast response for user interaction and that may experience bus
   13          contention and cacheline bounces as a result of timer interrupts.
   14          Note that the timer interrupt occurs on each processor in an SMP
   15          environment leading to NR_CPUS * HZ number of timer interrupts
   16          per second.
   17 
   18 
   19         config HZ_100
   20                 bool "100 HZ"
   21         help
   22           100 Hz is a typical choice for servers, SMP and NUMA systems
   23           with lots of processors that may show reduced performance if
   24           too many timer interrupts are occurring.
   25 
   26         config HZ_250
   27                 bool "250 HZ"
   28         help
   29          250 Hz is a good compromise choice allowing server performance
   30          while also showing good interactive responsiveness even
   31          on SMP and NUMA systems. If you are going to be using NTSC video
   32          or multimedia, selected 300Hz instead.
   33 
   34         config HZ_300
   35                 bool "300 HZ"
   36         help
   37          300 Hz is a good compromise choice allowing server performance
   38          while also showing good interactive responsiveness even
   39          on SMP and NUMA systems and exactly dividing by both PAL and
   40          NTSC frame rates for video and multimedia work.
   41 
   42         config HZ_1000
   43                 bool "1000 HZ"
   44         help
   45          1000 Hz is the preferred choice for desktop systems and other
   46          systems requiring fast interactive responses to events.
   47 
   48 endchoice
   49 
   50 config HZ
   51         int
   52         default 100 if HZ_100
   53         default 250 if HZ_250
   54         default 300 if HZ_300
   55         default 1000 if HZ_1000
   56 
   57 config SCHED_HRTICK
   58         def_bool HIGH_RES_TIMERS && (!SMP || USE_GENERIC_SMP_HELPERS)

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