On Mon, Apr 26, 2021 at 11:25 AM Vitaly Zaitsev via devel devel@lists.fedoraproject.org wrote:
On 25.04.2021 20:39, Artem Tim wrote:
Please provide full PREEMPT mode by default in 5.12 kernel for desktop variants. With 5.12 it is possible for user to change it without efforts if they need this.
+1 for this. Significantly reduces X11 input lag in full-screen games.
From a kernel standpoint, I do not think turning on CONFIG_PREEMPT is desired. That sets the *default* to PREEMPT, and changes the current situation. I plan to keep CONFIG_PREEMPT_VOLUNTARY as the default. The code introduced is odd, in that you can choose other options (none, voluntary, full) based on that starting point, but it doesn't allow you to default to anything else and keep CONFIG_PREEMPT_DYNAMIC on to choose more preemption than the default. I will see if I can hack something together and get it upstream that would allow us to keep the voluntary default and move to preempt with the command line. Moving forward, if something like that is not accepted, this might be a valid change for F35, but I don't see it reasonable to change preemption in stable releases (and the F34 ship has sailed). Even if I do get such a patch upstream, the default would remain voluntary, and the Desktop SIG could add a preempt= command line by default for F35+.
Justin