    PC. Co    DOS  -
   .    PIT  -
,          
HZ.       , ,  
,    .     
 86   APIC (Advanced Programmable Interrupt Controller,
   )    -
 (TSC, Time Stamp Counter).

  

,   ,   jiffies  HZ,     -
 ,     
.       : ,  
 ,   .

,     ,   -
      ,  -
  .  , ,    -
,      .

   xtime_lock,     -
 jiffies_64      xtime.

      ,   -
.

         -
 .

  -   do_timer ().

-  do_timer ()   
.

    jiffies_64   ( 
   32-  ,   
xtime_lock   ).

     ,   -
         ,  -
,     .

    ,    
  (     ).

   scheduler_tick (),      4.

    ,    

xtime.

       
(load average).

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