Hello Andrea, On Wed, Aug 28, 2024 at 08:20:50AM +0200, Andrea Righi wrote: > On Wed, Aug 28, 2024 at 10:38:45AM +0530, Gautham R. Shenoy wrote: > ... > > > I had thought this was a malfunction in the behavior that it reflected the > > > current status, not the hardware /capability/. > > > > > > Which one makes more sense for userspace? In my mind the most likely > > > consumer of this information would be something a sched_ext based userspace > > > scheduler. They would need to know whether the scheduler was using > > > preferred cores; not whether the hardware supported it. > > > > The commandline parameter currently impacts only the fair sched-class > > tasks since the preference information gets used only during > > load-balancing. > > > > IMO, the same should continue with sched-ext, i.e. if the user has > > explicitly disabled prefcore support via commandline, the no sched-ext > > scheduler should use the preference information to make task placement > > decisions. However, I would like to see what the sched-ext folks have > > to say. Adding some of them to the Cc list. > > IMHO it makes more sense to reflect the real state of prefcore support > from a "system" perspective, more than a "hardware" perspective, so if > it's disabled via boot command line it should show disabled. > > From a user-space scheduler perspective we should be fine either way, as > long as the ABI is clearly documented, since we also have access to > /proc/cmdline and we would be able to figure out if the user has > disabled it via cmdline (however, the preference is still to report the > actual system status). Thank you for confirming this. > > Question: having prefcore enabled affects also the value of > scaling_max_freq? Like an `lscpu -e`, for example, would show a higher > max frequency for the specific preferred cores? (this is another useful > information from a sched_ext scheduler perspective). Since the scaling_max_freq is computed based on the boost-numerator, at least from this patchset, the numerator would be the same across all kinds of cores, and thus the scaling_max_freq reported will be the same across all the cores. > > Thanks, > -Andrea -- Thanks and Regards gautham.
