Re: Microsecond sleeps with select()

Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
>> Having read the select(2) man page more closely, I now realize that
>> it is *defined* not to yield the processor when the requested delay
>> is zero: it just checks the file ready status and returns immediately.

> Actually, a kernel call is something. On kernel call return, process
> priorities are checked and the CPU may be yielded to a higher-priority
> backend that perhaps just had its I/O completed.

So *if* some I/O just completed, the call *might* do what we need,
which is yield the CPU. Otherwise we're just wasting cycles, and
will continue to waste them until we do a select with a nonzero
delay. I propose we cut out the spinning and just do a nonzero delay
immediately.

> I think the 0 and 10000 are correct. They would be zero ticks and one
> tick. You think 5000 and 10000 would be better? I can see that.

No, I am not suggesting that, because there is no difference between
5000 and 10000.

All of this stuff probably ought to be replaced with a less-bogus
mechanism (POSIX semaphores maybe?), but not in late beta.

regards, tom lane