Re: [PATCH] perf: fix interrupt handler timing harness

2013-07-08 Thread Stephane Eranian
On Mon, Jul 8, 2013 at 10:54 PM, Andi Kleen wrote: >> I did a quite a bit of ftracing to look for spots inside the handler >> which were taking large amounts of time. There were none. The >> execution time was spread very evenly over the entire nmi handler. It >> didn't appear to be any individ

Re: [PATCH] perf: fix interrupt handler timing harness

2013-07-08 Thread Andi Kleen
> I did a quite a bit of ftracing to look for spots inside the handler > which were taking large amounts of time. There were none. The > execution time was spread very evenly over the entire nmi handler. It > didn't appear to be any individual hot cachelines or doing something > silly like sitti

Re: [PATCH] perf: fix interrupt handler timing harness

2013-07-08 Thread Dave Hansen
On 07/08/2013 01:20 PM, Stephane Eranian wrote: > On Mon, Jul 8, 2013 at 10:05 PM, Dave Hansen wrote: >> 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

Re: [PATCH] perf: fix interrupt handler timing harness

2013-07-08 Thread Stephane Eranian
On Mon, Jul 8, 2013 at 10:05 PM, Dave Hansen wrote: > 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

Re: [PATCH] perf: fix interrupt handler timing harness

2013-07-08 Thread Dave Hansen
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 th

Re: [PATCH] perf: fix interrupt handler timing harness

2013-07-08 Thread Stephane Eranian
On Mon, Jul 8, 2013 at 4:34 PM, Dave Hansen wrote: > On 07/04/2013 03:30 PM, Stephane Eranian wrote: >> There was an misunderstanding on the API of the do_div() >> macro. It returns the remainder of the division and this >> was not what the function expected leading to disabling the >> interrupt l

Re: [PATCH] perf: fix interrupt handler timing harness

2013-07-08 Thread Dave Hansen
On 07/04/2013 03:30 PM, Stephane Eranian wrote: > There was an misunderstanding on the API of the do_div() > macro. It returns the remainder of the division and this > was not what the function expected leading to disabling the > interrupt latency watchdog. "Misunderstanding" is a very kind term f

Re: [PATCH] perf: fix interrupt handler timing harness

2013-07-04 Thread Ingo Molnar
* Stephane Eranian wrote: > This patch fixes a serious bug in: > > commit 14c63f17b1fde5a575a28e96547a22b451c71fb5 > Author: Dave Hansen > Date: Fri Jun 21 08:51:36 2013 -0700 > > perf: Drop sample rate when sampling is too slow > > > There was an misunderstanding on the API of th

[PATCH] perf: fix interrupt handler timing harness

2013-07-04 Thread Stephane Eranian
This patch fixes a serious bug in: commit 14c63f17b1fde5a575a28e96547a22b451c71fb5 Author: Dave Hansen Date: Fri Jun 21 08:51:36 2013 -0700 perf: Drop sample rate when sampling is too slow There was an misunderstanding on the API of the do_div() macro. It returns the remainder of th