High resolution sleep (Linux)

[John]

On 9 Maj, 03:23, John Nagle <n... at animats.com> wrote:
> Hendrik van Rooyen wrote:
> >  "Tim Roberts" <ti.. at pr...o.com> wrote"
> > It is also possible to keep the timer list sorted by "expiry date",
> > and to reprogram the timer to interrupt at the next expiry time
> > to give arbitrary resolution, instead of implementing a regular 'tick'.
>
>      Yes, and that's a common feature in real-time operating systems.
> If you're running QNX, you can expect that if your high priority
> task delays to a given time, you WILL get control back within a
> millisecond of the scheduled time.   Even tighter timing control
> is available on some non-x86 processors.
>
>      Some CPUs even have hardware support for a sorted event list.
> The Intel 8061, which ran the engines of most Ford cars in the 1980s,
> had that.
>
>      But no way are you going to get consistent timing resolution like that
> from Python.  It's an interpreter with a garbage collector, after all.
>
>                                 John Nagle


The application the original poster (i.e. me) was interested in was a
program that sends ethernet packets at a loosely specified rate. A
loop that sends all packets with no sleep in between will send them at
a too high rate. Using the default sleep in my Python interpreter
sleeps to long, since even a few microseconds add up when you send
hundreds of thousands of packets.

If the process scheduler deals with another process now and then, it
doesn't matter. If it switches to another application between each
packet is beeing sent, that's a problem.

Anyways, what I need is high resolution sleep, not high resolution
timing. Installing a real time OS seems like overkill.

(Yes I know, one can also send, say, 50 packets at a time, and then
sleep, send 50 more packets, and so on.)