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Name

init_timers, stamp_timers, diff_timers - routines to time sections

of your code

Synopsis


#include <timers.h>void init_timers(int maxtimers);void init_timers2(int maxtimers,
int mode);void stamp_timers(int slot);long long diff_timers(int slot1,
int slot2);double diff_timers2(int slot1, int slot2);

Description

init_timers is used to allocate a set of maxtimers slots to hold timer information. stamp_timers is used remember the timer info in a slot. The difference between slot2 and slot1 (slot2>slot1 is normally assumed) is returned by diff_timers.

init_timers2 (mode=1) was introduced to also use cputime(3NEMO) , at the slight cost of more ticks. diff_timers2 will report the difference in CPU seconds (not minutes!).

Timers use a low level assembly routine to directly accces the TSC (Time Stamp Counter), and have the usual flaws on multi proccesing cores and multi-tasking operating systems how to translate this to a CPU usage. For long term stability routines such as cputime(3NEMO) should be used,for short fine grained understanding, these routines could be useful.

This timers method approached something called Frame based profiling

Example

init_timers(n+1); for (i=0; i<n; i++)    stamp_timers(i);
stamp_timers(n) ; for (i=0; i<n; i++)    printf("Method-1: %Ld\n",diff_timers(i,i+1));

stamp_timers(0); for (i=0; i<n; i++) {    stamp_timers(i+1);
   printf("Method-2: %Ld\n",diff_timers(i,i+1));
}

Caveats

Currently this function is only implemented on Intel hardware, where it uses the Time Stamp Counter. It seems to work on AMD as well. For other processors 0 is returned.

long long is assumed to hold 64 bits, where unsigned is assumed 32 bit.

See Also

cputime(3NEMO) , clock(2) , time(2)

Author

Peter Teuben

Files


~/src/kernel/misc      timers.c

History


23-apr-04    created        PJT
25-feb-2024    added the cputime option    PJT

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