On Thu, Jun 19, 2014 at 10:45 PM, Stephane Eranian <eran...@google.com> wrote: > On Thu, Jun 19, 2014 at 10:40 PM, Andi Kleen <a...@linux.intel.com> wrote: >> On Thu, Jun 19, 2014 at 10:31:29PM +0200, Stephane Eranian wrote: >>> On Thu, Jun 19, 2014 at 10:18 PM, Andi Kleen <a...@linux.intel.com> wrote: >>> >> I don't quite understand that. >>> >> You need to know which events support PEBS. You need a table >>> > >>> > We're talking about the kernel allowing things here. >>> > Yes the user still needs to know what supports PEBS, but >>> > that doesn't concern the kernel. >>> > >>> Just need to make sure you don't return bogus information. >> >> GIGO. We only need to prevent security issues. >> >>> > You can just allow it for all, it's a nop if the event doesn't >>> > support it. And also the fields like DataLA are simply 0 when >>> > not supported. >>> > >>> >>> Let's take a example. If I do resource_stalls:pp, the kernel >>> will let it go through and clear the PMI bit on the config as >>> is required for PEBS mode. The counter will count normally >>> and never fire an interrupt, even when it overflows. It would >>> never execute the PMI handler and thus never look at the >>> PEBS content. You'd never get any samples. >> >> Yes if the user specifies a bogus raw event it will not count. >> That's fine. The important part is just that nothing ever crashes. >> > That would certainly avoid the problem of missing events in pebs table. > I had a problem with that just today. It also speed up scheduling > as well by avoid the table lookups. > I can take of writing the patch to do this, if you want.
> Note that I will soon post a patch to speed up scheduling for all x86 > processors. I'll put that one in too. -- 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/