sched: zap the migration init / cache-hot balancing code

the SMP load-balancer uses the boot-time migration-cost estimation
code to attempt to improve the quality of balancing. The reason for
this code is that the discrete priority queues do not preserve
the order of scheduling accurately, so the load-balancer skips
tasks that were running on a CPU 'recently'.

this code is fundamental fragile: the boot-time migration cost detector
doesnt really work on systems that had large L3 caches, it caused boot
delays on large systems and the whole cache-hot concept made the
balancing code pretty undeterministic as well.

(and hey, i wrote most of it, so i can say it out loud that it sucks ;-)

under CFS the same purpose of cache affinity can be achieved without
any special cache-hot special-case: tasks are sorted in the 'timeline'
tree and the SMP balancer picks tasks from the left side of the
tree, thus the most cache-cold task is balanced automatically.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 0 insertions, 11 deletions

diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 67edfa7ed93..a1b017f2dbb 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -51,16 +51,6 @@ int __cpu_logical_map[NR_CPUS];		/* Map logical to physical */
 EXPORT_SYMBOL(phys_cpu_present_map);
 EXPORT_SYMBOL(cpu_online_map);
 
-/* This happens early in bootup, can't really do it better */
-static void smp_tune_scheduling (void)
-{
-	struct cache_desc *cd = &current_cpu_data.scache;
-	unsigned long cachesize = cd->linesz * cd->sets * cd->ways;
-
-	if (cachesize > max_cache_size)
-		max_cache_size = cachesize;
-}
-
 extern void __init calibrate_delay(void);
 extern ATTRIB_NORET void cpu_idle(void);
 
@@ -228,7 +218,6 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 {
 	init_new_context(current, &init_mm);
 	current_thread_info()->cpu = 0;
-	smp_tune_scheduling();
 	plat_prepare_cpus(max_cpus);
 #ifndef CONFIG_HOTPLUG_CPU
 	cpu_present_map = cpu_possible_map;