• Ingo Molnar's avatar
    sched: zap the migration init / cache-hot balancing code · 0437e109
    Ingo Molnar authored
    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: default avatarIngo Molnar <mingo@elte.hu>
    0437e109
smp.c 9.53 KB