Re: [RFC][PATCH] new timeofday core subsystem (v.A0)

Christoph Lameter
2004-09-02T22:27:21Z

On Thu, 2 Sep 2004, john stultz wrote:

> +struct timesource_t {
> + char* name;
> + int priority;
> + cycle_t (*read)(void);
> + cycle_t (*delta)(cycle_t now, cycle_t then);
> + nsec_t (*cyc2ns)(cycle_t cycles, cycle_t* remainder);
> +};

This is defining functions to be called for a timesource. Which means that
the functionality for clock_gettime cannot be implemented as a fastcall
anymore on IA64. The delta and the cyc2ns function are always the same.
The compensation for jitter etc is always the same and can also be
implemented generically.

Could we change this to avoid the function calls.

For example.

struct timesource_t {
char *name;
int priority;
int type;
void *address;
long long int frequency;
}

The functions are always

delta = (now-then)
cycle2ns = cycles * (NSEC_PER_SEC / frequency) + remainder

types of time sources

#define TIMESOURCE_CPU 0
#define TIMESOURCE_MMIO32 1
#define TIMESOURCE_MMIO64 2
#define TIMESOURCE_FUNCTION 3 /* To catch odd cases */