On 05/03/2013 02:14 PM, Mike Galbraith wrote: > On Fri, 2013-05-03 at 13:57 +0800, Michael Wang wrote: >> Hi, Mike >> >> Thanks for your reply. >> >> On 05/03/2013 01:01 PM, Mike Galbraith wrote: >> [snip] >>>> >>>> If this approach caused any concerns, please let me know ;-) >>> >>> I wonder if throttling on failure is the way to go. Note the minimal >>> gain for pgbench with the default 1ms throttle interval. It's not very >>> effective out of the box for the load type it's targeted to help, and >>> people generally don't twiddle scheduler knobs. If you throttle on >>> success, you directly restrict migration frequency without that being >>> affected by what other tasks are doing. Seems that would be a bit more >>> effective. >> >> This is a good timing to make some conclusion for this problem ;-) >> >> Let's suppose when wake-affine failed, next time slice got a higher >> failure chance, then whether throttle on failure could be the question like: >> >> throttle interval should cover more failure timing >> or more success timing? >> >> Obviously we should cover more failure timing, since it's just wasting >> cycle and change nothing. >> >> However, I used to concern about the damage of succeed wake-affine at >> that rapid, sure it also contain the benefit, but which one is bigger? >> >> Now if we look at the RFC version which throttle on succeed, for >> pgbench, we could find that the default 1ms benefit is < 5%, while the >> current version which throttle on failure bring 7% at most. > > OK, so scratch that thought. Would still be good to find a dirt simple > dirt cheap way to increase effectiveness a bit, and eliminate the knob. > Until a better idea comes along, this helps pgbench some, and will also > help fast movers ala tbench on AMD, where select_idle_sibling() wasn't > particularly wonderful per my measurements.
Yep, another advantage of this approach is simple, when later we figure out the better idea, it could be easily replaced, for now, I would prefer to use it as an urgent rescue for the 'suffered workload' ;-) Regards, Michael Wang > > -Mike > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
