Messages in this thread | | | Date | Mon, 28 Jan 2019 09:23:13 +0100 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH v1 3/3] drivers/tty: increase priority for tty_buffer_worker |
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On Mon, Jan 28, 2019 at 09:05:30AM +0100, Oleksij Rempel wrote: > > > On 10.01.19 17:30, Greg Kroah-Hartman wrote: > > On Thu, Jan 10, 2019 at 04:19:53PM +0100, Oleksij Rempel wrote: > > > > My gut feel is that if somebody still cares deeply about serial line > > > > latency, they should look at trying to see if they can do some of the > > > > work directly without the bounce to the workqueue. We use workqueues > > > > for a reason, but it's possible that some of it could be avoided at > > > > least in special cases... And yours sounds like a special case. > > > > > > It is for industrial low latency RS-422 based application. The loopback > > > test is just easy way to test/reproduce it without additional hardware. > > > > > > What is good, mainlineable way to implement it? > > > > What is the real problem your systems are having? Are they serial-port > > limited? Is latency a big issue? Trying to tune for a fake workload > > isn't the best way to solve anything :) > > The system in question is a high power laser cutter with live image-based inspection > and adjustment of the cutting process. In this setup the RS422 interface is used to > control parameters of the laser cutting unit in a tie control loop with the camera. > This loops needs to operate at 1000 Hz. > > The xy-stage moves with a speed of approx. 60m/min, i.e. within 1ms it > moves about 1mm. For a high precision control process a jitter of ± 500 us (+/- 0.5mm) > is unacceptable.
Are you using the rt kernel patch for this type of thing? That should bound your jitter at a much more deterministic level.
thanks,
greg k-h
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