On Friday 16 February 2001 12:40, Alex Lin wrote:
> Hi all,
>
> Can someone give me a simple example how can I get a higher resolution
> time without RTLinux? I just want to compare the latency between the
> regular linux procedure and RTLinux procedure.
Do you need something like "interrupts", or just an accurate source of
timestamps?
For the former, apply the UTIME patch, or use the RTC device to generate
timing for your thread. Audio cards can also be "abused" at time base
generators in this way.
If you just need timestamps and have a Pentium or better x86 CPU, the easiest
way is probably to read the TSC. It counts core clock cycles, is 64 bits wide
and is read with a single machine code instruction. Here's a macro to do that:
---8<----------------------------------------------------------
__inline__ unsigned long long int rdtsc(void)
{
unsigned long long int x;
__asm__ volatile (".byte 0x0f, 0x31" : "=A" (x));
return x;
}
---------------------------------------------------------->8---
Grab the CPU clock from /proc/cpuinfo; the "cpu MHz" line, to translate into
more useful units.
//David
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.- David Olofson -------------------------------------------.
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