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authorIngo Molnar <mingo@elte.hu>2007-07-09 12:51:57 -0400
committerIngo Molnar <mingo@elte.hu>2007-07-09 12:51:57 -0400
commit0437e109e1841607f2988891eaa36c531c6aa6ac (patch)
treee9d8f170786f7e33d4c5829cb008cf38d42a2014 /arch/i386
parent0e6aca43e08a62a48d6770e9a159dbec167bf4c6 (diff)
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>
Diffstat (limited to 'arch/i386')
-rw-r--r--arch/i386/kernel/smpboot.c12
1 files changed, 0 insertions, 12 deletions
diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index 88baed1e7e83..0b2954534b8e 100644
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -941,17 +941,6 @@ exit:
941} 941}
942#endif 942#endif
943 943
944static void smp_tune_scheduling(void)
945{
946 if (cpu_khz) {
947 /* cache size in kB */
948 long cachesize = boot_cpu_data.x86_cache_size;
949
950 if (cachesize > 0)
951 max_cache_size = cachesize * 1024;
952 }
953}
954
955/* 944/*
956 * Cycle through the processors sending APIC IPIs to boot each. 945 * Cycle through the processors sending APIC IPIs to boot each.
957 */ 946 */
@@ -980,7 +969,6 @@ static void __init smp_boot_cpus(unsigned int max_cpus)
980 x86_cpu_to_apicid[0] = boot_cpu_physical_apicid; 969 x86_cpu_to_apicid[0] = boot_cpu_physical_apicid;
981 970
982 current_thread_info()->cpu = 0; 971 current_thread_info()->cpu = 0;
983 smp_tune_scheduling();
984 972
985 set_cpu_sibling_map(0); 973 set_cpu_sibling_map(0);
986 974