On 20-05-15, 15:09, Thomas Gleixner wrote: > On Wed, 20 May 2015, Viresh Kumar wrote:
> They look at clock_event_mode and not at state, right? Yeah, it was all useful (that's what I thought initially, but not anymore) only when we migrate some drivers to the new per-state APIs. > And that way we add the overhead of a full function call to those > drivers for the interrupt hot path? Honestly, I didn't realize that this can be a blocker. My bad. > Of course you should have done that analysis before posting some > random helper functions. I did looked at all the drivers few days back, but failed to give a summary similar to yours. No excuses. > Lets look how useful these functions are for the various use cases > > #1) Adds function call over head to the timer interrupt > > Hot path does matter and that function call is a regression. So > that's a NONO > Now explain me how your magic functions help. For most of the cases > they would be a performance regression. And for the rest they really > do not matter at all. They wouldn't help at all in that case. So, probably we are left with following choices: - Maintain state internally within the driver. SMP cases need per-cpu storage as clkevt devices are per-cpu. Probably that's a NONO as well ? - Use CLK_EVT_STATE_* directly in drivers (similar to the way we use CLK_EVT_MODE_* today). - Write the routines I proposed as macros or inline functions in clockchips.h, and use them. Of course that wouldn't stop exposing CLK_EVT_STATE_* to rest of the kernel. - Something else ? Which one do you suggest ? -- viresh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
