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

On 2015/10/22 11:09, Alexei Starovoitov wrote:

On 10/21/15 6:56 PM, Wangnan (F) wrote:

quoted

quoted

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.

What pt_regs would be in such case?

Sampling is based on interruption. We can use pt_reg captured by the IRQ 
handler,
or we can simply pass NULL to those BPF program.

Thank you.