• Paolo Valente's avatar
    block, bfq: remove slow-system class · e24f1c24
    Paolo Valente authored
    BFQ computes the duration of weight raising for interactive
    applications automatically, using some reference parameters. In
    particular, BFQ uses the best durations (see comments in the code for
    how these durations have been assessed) for two classes of systems:
    slow and fast ones. Examples of slow systems are old phones or systems
    using micro HDDs. Fast systems are all the remaining ones. Using these
    parameters, BFQ computes the actual duration of the weight raising,
    for the system at hand, as a function of the relative speed of the
    system w.r.t. the speed of a reference system, belonging to the same
    class of systems as the system at hand.
    
    This slow vs fast differentiation proved to be useful in the past, but
    happens to have little meaning with current hardware. Even worse, it
    does cause problems in virtual systems, where the speed of the system
    can vary frequently, and so widely to just confuse the class-detection
    mechanism, and, as we have verified experimentally, to cause BFQ to
    compute non-sensical weight-raising durations.
    
    This commit addresses this issue by removing the slow class and the
    class-detection mechanism.
    Signed-off-by: 's avatarPaolo Valente <paolo.valente@linaro.org>
    Signed-off-by: 's avatarJens Axboe <axboe@kernel.dk>
    e24f1c24