example:vi ...linux/param.h #ifndef _LINUX_PARAM_H #define _LINUX_PARAM_H #includevi /hda4/usr/include/asm/param.h #ifndef _ASMi386_PARAM_H #define _ASMi386_PARAM_H #ifndef HZ #define HZ 100 #endif
kernel uses it to keep track of time intervals.
architecture dependent value defined in linux/param.h
1024 for alpha; 100 for all other platforms
timer interrupt increments "jiffies" value.
therefore "jiffies" is the number of clock ticks since GNUX was booted.
declared in linux/sched.h
>> ulongs=2^32 ulongs = 4.2950e+09 >> seconds=ulongs/100 seconds = 4.2950e+07 >> hours=seconds/3600 hours = 1.1930e+04 >> days=hours/24 days = 497.1027e.g. can't have more than 498 days uptime.
ordinarily with "toy" operating systems that crash several times a day, that's not a problem, but GNUX is actually so reliable that the above limit is a problem.
solution: buy a dec alpha:
>> ulongs=2^64 ulongs = 1.8447e+19 >> seconds=ulongs/100 seconds = 1.8447e+17 >> hours=seconds/3600 hours = 5.1241e+13 >> days=hours/24 days = 2.1350e+12 >> years=days/365.242 years = 5.8455e+09uptime: more than 5 billion years.
100 is probably the best value for most things.
reduce to extend uptime but computer sluggish;
10k gives less than 5 days uptime.
increasing doesn't necessarily make computer go faster (e.g. more time spent in servicing interrupts, etc.)
warning: if you change this value you must recompile and reinstall all modules.