On Thu, Jun 22, 2023 at 12:33:31PM +0200, Juergen Gross wrote: > On 22.06.23 10:26, Peter Zijlstra wrote:
> > > The downside would be that some workloads might see worse performance > > > due to backend I/O handling might get preempted. > > > > Is that an actual concern? Mark this a legaxy inteface and anybody who > > wants to get away from it updates. > > It isn't that easy. See above. Well, the old stuff gets to use full preemption on Dom0, then the new stuff gets more shiny options. > > > Just thinking - can full preemption be enabled per process? > > > > Nope, that's a system wide thing. Preemption is something that's driven > > by the requirements of the tasks that preempt, not something by the > > tasks that get preempted. > > Depends. If a task in a non-preempt system could switch itself to be > preemptable, we could do so around hypercalls without compromising the > general preemption setting. Disabling preemption in a preemptable system > should continue to be possible for short code paths only, of course. So something along those lines was suggested elsewhere, and I'm still not entirely sure how I feel about it, but look here: https://lkml.kernel.org/r/20230403052233.1880567-1-ankur.a.ar...@oracle.com Specifically patches 7 and 8. It is very close so that you currently do/want. Those patches are many moons old and i've not seen an update on them, so I've no idea where they are. It solves a similar problem except it is 'rep string' instructions that's being interrupted.
