On 07/08/2013 11:08 AM, Stephane Eranian wrote: > I admit I have some issues with your patch and what it is trying to avoid. > There is already interrupt throttling. Your code seems to address latency > issues on the handler rather than rate issues. Yet to mitigate the latency > it is modify the throttling.
If we have too many interrupts, we need to drop the rate (existing throttling). If the interrupts _consistently_ take too long individually they can starve out all the other CPU users. I saw no way to make them finish faster, so the only recourse is to also drop the rate. > For some unknown reasons, my HSW interrupt handler goes crazy for > a while running a very simple: > $ perf record -e cycles branchy_loop > > And I do see in the log: > perf samples too long (2546 > 2500), lowering > kernel.perf_event_max_sample_rate to 50000 > > Which is an enormous latency. I instrumented the code, and under > normal conditions the latency > of the handler for this perf run, is about 500ns and it is consistent > with what I see on SNB. I was seeing latencies near 1 second from time to time, but _consistently_ in the hundreds of milliseconds. -- 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/
