Re: [PATCH 2/5] ftrace perf: Move exclude_kernel tracepoint check to init event

From	Jiri Olsa <jolsa@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/5] ftrace perf: Move exclude_kernel tracepoint check to init event
Date	2016-03-24 13:30 +0100
Message-ID	<rgcyK-2B9-7@gated-at.bofh.it> (permalink)
References	<rdkMa-1Kx-7@gated-at.bofh.it> <rdkMa-1Kx-23@gated-at.bofh.it> <rfOPL-2sH-1@gated-at.bofh.it> <rgadB-EQ-15@gated-at.bofh.it> <rgb9E-1lm-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Mar 24, 2016 at 11:49:34AM +0100, Peter Zijlstra wrote:
> On Thu, Mar 24, 2016 at 10:56:48AM +0100, Jiri Olsa wrote:
> > On Wed, Mar 23, 2016 at 11:41:29AM +0100, Peter Zijlstra wrote:
> > > On Wed, Mar 16, 2016 at 03:34:30PM +0100, Jiri Olsa wrote:
> > > > We suppress events with attr::exclude_kernel set when
> > > > the event is generated, so following capture will
> > > > give no warning but won't produce any data:
> > > > 
> > > >   $ sudo perf record -e sched:sched_switch:u ls
> > > >   $ sudo /perf script | wc -l
> > > >   0
> > > > 
> > > > Checking the attr::exclude_(kernel|user) at the event
> > > > init time and failing right away for tracepoints from
> > > > uprobes/kprobes and native ones:
> > > > 
> > > >   $ sudo perf record -e sched:sched_switch:u ls
> > > >   Error:
> > > >   The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (sched:sched_switch).
> > > >   /bin/dmesg may provide additional information.
> > > >   No CONFIG_PERF_EVENTS=y kernel support configured?
> 
> > > Not sure about this one. The previous behaviour suggests
> > > exclude_{user,kernel} is implemented, while the new behaviour says these
> > > flags are not implemented, which is a functional regression.
> > 
> > well I would not expect 'sched:sched_switch:u' to work (be implemented)
> > 
> > and I thought it's better to trigger an error than silently 'produce' no data
> 
> We're not in the business of protecting people from themselves are we?
> And if you want to help them, do so in userspace.

yep, I planned to make user space patch
to make that error more user friendly

> 
> And its not like the [uk] flags are hard to implement here.

sched:sched_switch:u ?

jirka

Thread

Re: [PATCH 2/5] ftrace perf: Move exclude_kernel tracepoint check to  init event Peter Zijlstra <peterz@infradead.org> - 2016-03-23 12:10 +0100
  Re: [PATCH 2/5] ftrace perf: Move exclude_kernel tracepoint check to  init event Jiri Olsa <jolsa@redhat.com> - 2016-03-24 11:00 +0100
    Re: [PATCH 2/5] ftrace perf: Move exclude_kernel tracepoint check to  init event Peter Zijlstra <peterz@infradead.org> - 2016-03-24 12:00 +0100
      Re: [PATCH 2/5] ftrace perf: Move exclude_kernel tracepoint check to  init event Jiri Olsa <jolsa@redhat.com> - 2016-03-24 13:30 +0100
        Re: [PATCH 2/5] ftrace perf: Move exclude_kernel tracepoint check to  init event Peter Zijlstra <peterz@infradead.org> - 2016-03-24 14:10 +0100
          Re: [PATCH 2/5] ftrace perf: Move exclude_kernel tracepoint check to  init event Jiri Olsa <jolsa@redhat.com> - 2016-03-24 14:40 +0100

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