Messages in this thread | | | Date | Thu, 10 Jan 2019 16:19:53 +0100 | From | Oleksij Rempel <> | Subject | Re: [PATCH v1 3/3] drivers/tty: increase priority for tty_buffer_worker |
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On Thu, Jan 10, 2019 at 04:54:53AM -0800, Linus Torvalds wrote: > On Thu, Jan 10, 2019 at 2:12 AM Oleksij Rempel <o.rempel@pengutronix.de> wrote: > > > > sched_priority = 1 is enough to dramatically reduce latency > > on have system load produced by tasks with default user space prio. > > .. and is this perhaps a way for a user to then make the system spend > inordinate amounts of time in the tty layer, and hurting other people? > I'm thinking threads using pty's etc as a way to make the system > unresponsive. > > We have *never* had good results with random priority modifications. > People used to do this for the X server, and it helped in very > specific cases, and hurt enormously in others. > > Why would anybody use a tty interface with a l;oopback adapter and > care about latency? > > I can kind of see why you want to do this from a theoretical point, > but from a *practical* point of view it seems pointless. Why not use > more appropriate models like networking or pipes etc. IOW, I think you > should describe what you *really* are doing much more. > > "hackbench with a loopback serial adapter" really doesn't sound like > something that should worry a lot of people.
yes, you right.
> 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?
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