Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling
Date	2015-10-22 11:50 +0200
Message-ID	<qmkFu-6UJ-53@gated-at.bofh.it> (permalink)
References	(5 earlier) <qm0x4-2Fy-21@gated-at.bofh.it> <qm1Wa-4CG-11@gated-at.bofh.it> <qmdui-4Se-13@gated-at.bofh.it> <qmeqm-6lm-11@gated-at.bofh.it> <qmeA2-6wC-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Oct 22, 2015 at 11:12:16AM +0800, Wangnan (F) wrote:
> On 2015/10/22 11:09, Alexei Starovoitov wrote:
> >On 10/21/15 6:56 PM, Wangnan (F) wrote:
> >>>One alternative solution I can image is to attach a BPF program
> >>>at sampling like kprobe, and return 0 if we don't want sampling
> >>>take action. Thought?
> >>
> >>Do you think attaching BPF programs to sampling is an acceptable idea?
> >
> >If you mean to extend 'filter' concept to sampling events?
> >So instead of soft_disable of non-local events, you'll attach bpf
> >program to sampling events and use map lookup to decide whether
> >to filter out or not such sampling event?
> 
> Yes.

One could overload or stack the overflow handler I suppose. But this
would be in line with the software/tracepoint events calling eBPF muck
on trigger, right?

> >What pt_regs would be in such case?

> Sampling is based on interruption. We can use pt_reg captured by the IRQ
> handler,

s/IRQ/NMI/

Also, we 'edit' the pt_regs on the way down to the overflow handler as
sometimes 'better' information can be had from PMU state. But a pt_regs
is available there.
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Thread

[PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling Kaixu Xia <xiakaixu@huawei.com> - 2015-10-20 09:30 +0200
  Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Alexei Starovoitov <ast@plumgrid.com> - 2015-10-21 01:00 +0200
    Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 11:20 +0200
      Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling xiakaixu <xiakaixu@huawei.com> - 2015-10-21 12:40 +0200
        Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 13:40 +0200
          Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-21 14:00 +0200
            Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 14:20 +0200
              Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-21 15:50 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 16:00 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling pi3orama <pi3orama@163.com> - 2015-10-21 16:10 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 16:10 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling pi3orama <pi3orama@163.com> - 2015-10-21 17:20 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 19:00 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Alexei Starovoitov <ast@plumgrid.com> - 2015-10-21 23:30 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-22 11:10 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-22 12:40 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-23 15:00 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-23 17:20 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling xiakaixu <xiakaixu@huawei.com> - 2015-10-27 07:50 +0100
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-22 05:00 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Ingo Molnar <mingo@kernel.org> - 2015-10-22 09:50 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-22 10:00 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-22 11:30 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-22 04:10 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Alexei Starovoitov <ast@plumgrid.com> - 2015-10-22 05:10 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-22 05:20 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Alexei Starovoitov <ast@plumgrid.com> - 2015-10-22 05:30 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-22 11:50 +0200
      Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-21 13:40 +0200
        Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 14:00 +0200
          Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-21 14:10 +0200

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