Quoting Douglas Anderson (2020-04-22 14:55:03) > It has been postulated that the pm_lock is bad for performance because > a CPU currently running rpmh_flush() could block other CPUs from > coming out of idle. Similarly CPUs coming out of / going into idle > all need to contend with each other for the spinlock just to update > the variable tracking who's in PM. > > Let's optimize this a bit. Specifically: > > - Use a count rather than a bitmask. This is faster to access and > also means we can use the atomic_inc_return() function to really > detect who the last one to enter PM was. > - Accept that it's OK if we race and are doing the flush (because we > think we're last) while another CPU is coming out of idle. As long > as we block that CPU if/when it tries to do an active-only transfer > we're OK. > > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> > --- Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
