On Thu Nov 29 04:20:52 EST 2012, [email protected] wrote:
> My problem is that the kernel is not currently capable of supplying
> what Erik defines, to the process level even internally, and even for
> his described applications (delays of a small interval, tiny
> retransmission times), it's not clear that the traditional sleep,
> which has *always* been sloppy, is anyway the right model; and
> certainly not for any more general application. I had a quick read
> through some papers and theses last night, and it certainly isn't
> clear cut.
i ran a little test. the meat of the program is this
cycles(t+0);
for(i = 0; i < 5000000000ull; i += s)
nsleep(s);
cycles(t+1);
print("%g\n", cyclestoseconds(t[1]-t[0]));
i get quite predictable results; there is no cliff.
sleep in ns elapsed time calculated syscall overhead
1000000000 5.000012 # 2.40µs / syscall
100000000 5.000106 # 2.12µs / syscall
10000000 5.001097 # 2.19µs / syscall
1000000 5.01078 # 2.16µs / syscall
100000 5.102487 # 2.16µs / syscall
10000 6.081568 # 2.16µs / syscall
- erik
