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

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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>
This commit is contained in:
Ingo Molnar 2007-07-09 18:51:57 +02:00
parent 0e6aca43e0
commit 0437e109e1
8 changed files with 0 additions and 596 deletions
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10
arch/sparc/kernel/smp.c
View file

@ -68,16 +68,6 @@ void __cpuinit smp_store_cpu_info(int id)
cpu_data(id).prom_node = cpu_node;
cpu_data(id).mid = cpu_get_hwmid(cpu_node);
/* this is required to tune the scheduler correctly */
/* is it possible to have CPUs with different cache sizes? */
if (id == boot_cpu_id) {
int cache_line,cache_nlines;
cache_line = 0x20;
cache_line = prom_getintdefault(cpu_node, "ecache-line-size", cache_line);
cache_nlines = 0x8000;
cache_nlines = prom_getintdefault(cpu_node, "ecache-nlines", cache_nlines);
max_cache_size = cache_line * cache_nlines;
}
if (cpu_data(id).mid < 0)
panic("No MID found for CPU%d at node 0x%08d", id, cpu_node);
}