On Mon, 12 Oct 2015, Frederic Weisbecker wrote: > This reverts commit 8cb9764fc88b41db11f251e8b2a0d006578b7eb4. > > We assumed that nohz full users always want scheduler isolation on full > dynticks CPUs, therefore we included nohz full CPUs on cpu_isolated_map. > This means that tasks run by default on CPUs outside the nohz_full range > unless their affinity is explicity overwritten. > > This suits pure isolation workloads but when the machine is needed to > run common workloads, the available sets of CPUs to run common tasks > becomes reduced. > > We reach an extreme case when CONFIG_NO_HZ_FULL_ALL is enabled as it > leaves only CPU 0 for non-isolation tasks, which makes people think that > their supercomputer regressed to 90's UP. > > Some nohz full users appear to be interested in running normal workloads > either before or after an isolation workload. Nohz full isn't optimized > toward normal workloads but it's still better than UP performance. > > We are reaching a limitation in kernel presets here. Lets revert this > cpu_isolated_map inclusion and let userspace do its own scheduler > isolation using cpusets or explicit affinity settings.
Acked-by: Thomas Gleixner <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
