• Peter Zijlstra's avatar
    sched: Remove stale power aware scheduling remnants and dysfunctional knobs · 8e7fbcbc
    Peter Zijlstra authored
    It's been broken forever (i.e. it's not scheduling in a power
    aware fashion), as reported by Suresh and others sending
    patches, and nobody cares enough to fix it properly ...
    so remove it to make space free for something better.
    
    There's various problems with the code as it stands today, first
    and foremost the user interface which is bound to topology
    levels and has multiple values per level. This results in a
    state explosion which the administrator or distro needs to
    master and almost nobody does.
    
    Furthermore large configuration state spaces aren't good, it
    means the thing doesn't just work right because it's either
    under so many impossibe to meet constraints, or even if
    there's an achievable state workloads have to be aware of
    it precisely and can never meet it for dynamic workloads.
    
    So pushing this kind of decision to user-space was a bad idea
    even with a single knob - it's exponentially worse with knobs
    on every node of the topology.
    
    There is a proposal to replace the user interface with a single
    3 state knob:
    
     sched_balance_policy := { performance, power, auto }
    
    where 'auto' would be the preferred default which looks at things
    like Battery/AC mode and possible cpufreq state or whatever the hw
    exposes to show us power use expectations - but there's been no
    progress on it in the past many months.
    
    Aside from that, the actual implementation of the various knobs
    is known to be broken. There have been sporadic attempts at
    fixing things but these always stop short of reaching a mergable
    state.
    
    Therefore this wholesale removal with the hopes of spurring
    people who care to come forward once again and work on a
    coherent replacement.
    Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Suresh Siddha <suresh.b.siddha@intel.com>
    Cc: Arjan van de Ven <arjan@linux.intel.com>
    Cc: Vincent Guittot <vincent.guittot@linaro.org>
    Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Link: http://lkml.kernel.org/r/1326104915.2442.53.camel@twinsSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    8e7fbcbc
cpu.c 8.22 KB