[ST-users] _st_epoll_dispatch firing too often

[CN <cu...@ya...>]

_st_epoll_dispatch seems to fire too often when the sleepq is not empty. 
My guess is that it has something to do with granularity.
Here's some basic code to reproduce:

#include <stdio.h>
#include "st.h"
int main(int argc, char *argv[])

{
    st_utime_t t1, t2;
    st_set_eventsys(ST_EVENTSYS_ALT);
    st_init();
    for (;;) {

        t1 = st_utime();
        st_sleep(1);
        t2 = st_utime();
        fprintf(stderr, "%p MAIN diff = %llu\n", st_thread_self(), t2 - t1);
    }
    return 0;

}


And add some logging to event.c @ line 1244.
ie.
1243:  timeout = (int) (min_timeout / 1000);
1244:  if (timeout == 0 && _ST_SLEEPQ->due > _ST_LAST_CLOCK)
1245:      fprintf(stderr, "%p ST   diff=%llu\n", _ST_SLEEPQ, _ST_SLEEPQ->due - _ST_LAST_CLOCK);
1245: }

You'll also need "#include <stdio.h>" .


If you run the test, you'll see something like:
0x805f068 MAIN diff = 999992
0x805f068 ST   diff=241
0x805f068 ST   diff=222
0x805f068 ST   diff=210
0x805f068 ST   diff=199
0x805f068 ST   diff=188
0x805f068 ST   diff=177
0x805f068 ST   diff=166
0x805f068 ST   diff=155
0x805f068 ST   diff=144
0x805f068 ST   diff=133
0x805f068 ST   diff=122
0x805f068 ST   diff=111
0x805f068 ST   diff=100
0x805f068 ST   diff=89
0x805f068 ST   diff=78
0x805f068 ST   diff=66
0x805f068 ST   diff=55
0x805f068 ST   diff=44
0x805f068 ST   diff=33
0x805f068 ST   diff=23
0x805f068 ST   diff=12
0x805f068 ST   diff=1
0x805f068 MAIN diff = 1000000



The unnecessary firing gets worse when the sleepq gets longer.
My "fix" for this is to put a limit on the timeout, like so:
if (_ST_SLEEPQ->due <= _ST_LAST_CLOCK) {
    timeout = 0;
} else {
    min_timeout = _ST_SLEEPQ->due - _ST_LAST_CLOCK;
    if (min_timeout < 300) /* magic number 300 seems to work well */
        timeout = 1;
    else
        timeout = (int) (min_timeout / 1000);
}

Is this a bug or am I using st-threads incorrectly?
If it's a bug, is there a better way to fix it without using magic numbers?


Regards,
C.