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Groups > linux.kernel > #1645472
| From | Will Deacon <will.deacon@arm.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified |
| Date | 2017-05-19 11:50 +0200 |
| Message-ID | <tIMHM-hj-17@gated-at.bofh.it> (permalink) |
| References | <tIFPY-3RD-9@gated-at.bofh.it> <tIMoq-8v4-11@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Fri, May 19, 2017 at 11:29:05AM +0200, Peter Zijlstra wrote:
> On Fri, May 19, 2017 at 06:19:12PM +0800, Jin Yao wrote:
> > +bool skid_kernel_samples(struct perf_event *event, struct pt_regs *regs)
> > +{
> > + u64 ip;
> > +
> > + /*
> > + * Without PEBS, we may get kernel samples even though
> > + * exclude_kernel is specified due to skid in sampling.
> > + */
> > + if ((event->attr.exclude_kernel) &&
> > + (event->attr.sample_type & PERF_SAMPLE_IP)) {
> > + ip = perf_instruction_pointer(regs);
> > + if (kernel_ip(ip))
> > + return true;
> > + }
> > +
> > + return false;
> > +}
> > +
> > EVENT_ATTR(cpu-cycles, CPU_CYCLES );
> > EVENT_ATTR(instructions, INSTRUCTIONS );
> > EVENT_ATTR(cache-references, CACHE_REFERENCES );
>
>
> I would much rather see this in generic code, somewhere around
> __perf_event_overflow() I suppose. That would retain proper accounting
> for the interrupt rate etc..
>
> Also it would work for all architectures. Because I'm thinking more than
> just x86 will suffer from skid.
Yes, I think this will affect arm/arm64 too (and probably others that rely
on irqs for sampling the regs).
Will
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[PATCH] perf/x86/intel: Drop kernel samples even though :u is specified Jin Yao <yao.jin@linux.intel.com> - 2017-05-19 04:30 +0200
Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified Peter Zijlstra <peterz@infradead.org> - 2017-05-19 11:30 +0200
Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified Will Deacon <will.deacon@arm.com> - 2017-05-19 11:50 +0200
Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified "Jin, Yao" <yao.jin@linux.intel.com> - 2017-05-19 14:10 +0200
Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified Peter Zijlstra <peterz@infradead.org> - 2017-05-19 14:20 +0200
Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified "Jin, Yao" <yao.jin@linux.intel.com> - 2017-05-19 14:30 +0200
Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified Peter Zijlstra <peterz@infradead.org> - 2017-05-19 14:40 +0200
Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified "Jin, Yao" <yao.jin@linux.intel.com> - 2017-05-19 15:40 +0200
Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified "Jin, Yao" <yao.jin@linux.intel.com> - 2017-05-22 04:20 +0200
Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified Mark Rutland <mark.rutland@arm.com> - 2017-05-22 10:50 +0200
Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified Peter Zijlstra <peterz@infradead.org> - 2017-05-22 11:30 +0200
Re: [PATCH] perf/x86/intel: Drop kernel samples even though :u is specified "Jin, Yao" <yao.jin@linux.intel.com> - 2017-05-22 14:40 +0200
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