Re: [PATCH 0/3] Add PERF_EVENT_IOC_QUERY_KPROBE ioctl

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On Wed, Aug 7, 2019, at 12:03 PM, Andrii Nakryiko wrote:
> On Tue, Aug 6, 2019 at 4:39 PM Daniel Xu <dxu@xxxxxxxxx> wrote:
> >
> > It's useful to know kprobe's nmissed and nhit stats. For example with
> 
> Is nmissed/nhit kprobe-specific? What about tracepoints and raw
> tracepoints, do they have something similar or they can never be
> missed? At least nhit still seems useful, so would be nice to have
> ability to get that with the same API, is it possible?
> 

I'm still trying to grok all the tracepoint/ftrace machinery, but it appears
to me like it is kprobe/uprobe specific. My guess is that b/c tracepoints are
inline (and don't require trapping interrupts), it cannot really "miss".

This brings up a good point, though. I think we want the same querying
functionality for uprobes so it might be worthwhile to make this API generic.
Something like PERF_EVENT_IOC_QUERY_PROBE so we can later add in
uprobe stats. And maybe tracepoint if it makes sense.

Thoughts?



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