Messages in this thread | | | Date | Thu, 20 Feb 2014 17:06:08 -0500 | From | Peter Hurley <> | Subject | Re: locking changes in tty broke low latency feature |
| |
On 02/20/2014 02:33 PM, Grant Edwards wrote: > On 2014-02-20, Peter Hurley <peter@hurleysoftware.com> wrote: >> Sender completes 2000 loops in 160ms total run time; >> that's 80us average per complete round-trip. > > If I understand correctly, that 80us _includes_ the actual time for > the bits on the wire (which means the actual "baud rate" involved is > high enough that it's negligible).
Yes, 80us includes the transmit time.
>> I think this shows that low_latency is unnecessary and should >> just be removed/ignored by the tty core. > > If that's the sort of latency that you get for typical kernel > configurations for typical distros, then I agree that the low_latency > flag is not needed by the tty later.
Stock ubuntu kernel config but preempt and 250hz (and debugging stuff).
> However, it might still be useful for the lower-level tty or > serial-core driver to control CPU usage vs. latency trade-offs (for > exaple, one of my drivers uses it to decide where to set the rx FIFO > threshold).
Sure, it could be left for driver consumption.
Regards, Peter Hurley
| |