On Tue, Feb 23, 2016 at 2:22 AM, Steve Muckle <[email protected]> wrote: > From: Michael Turquette <[email protected]> > > Some architectures and platforms perform CPU frequency transitions > through a non-blocking method, while some might block or sleep. Even > when frequency transitions do not block or sleep they may be very slow. > This distinction is important when trying to change frequency from > a non-interruptible context in a scheduler hot path. > > Describe this distinction with a cpufreq driver flag, > CPUFREQ_DRIVER_FAST. The default is to not have this flag set, > thus erring on the side of caution. > > cpufreq_driver_is_slow() is also introduced in this patch. Setting > the above flag will allow this function to return false. > > [[email protected]: change flag/API to include drivers that are too > slow for scheduler hot paths, in addition to those that block/sleep] > > Cc: Rafael J. Wysocki <[email protected]> > Cc: Viresh Kumar <[email protected]> > Signed-off-by: Michael Turquette <[email protected]> > Signed-off-by: Steve Muckle <[email protected]>
Something more sophisticated than this is needed, because one driver may actually be able to do "fast" switching in some cases and may not be able to do that in other cases. For example, in the acpi-cpufreq case all depends on what's there in the ACPI tables. Thanks, Rafael
