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. Reported-by: Ingo Molnar <[email protected]> Reported-by: Mike Galbraith <[email protected]> Cc: Chris Metcalf <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Dave Jones <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Alexey Dobriyan <[email protected]> Cc: Andrew Morton <[email protected]> Signed-off-by: Frederic Weisbecker <[email protected]> --- kernel/sched/core.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 6159531..3c35b5f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7238,9 +7238,6 @@ void __init sched_init_smp(void) alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL); alloc_cpumask_var(&fallback_doms, GFP_KERNEL); - /* nohz_full won't take effect without isolating the cpus. */ - tick_nohz_full_add_cpus_to(cpu_isolated_map); - sched_init_numa(); /* -- 2.5.3 -- 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/
