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    SubjectRe: [RFC] perf/core: allow ftrace for functions in kernel/event/core.c
    On Tue, 26 May 2020 21:46:29 +0000
    Song Liu <songliubraving@fb.com> wrote:

    >
    >
    > > On May 26, 2020, at 2:39 PM, Peter Zijlstra <peterz@infradead.org> wrote:
    > >
    > > On Tue, May 26, 2020 at 02:28:26PM -0700, Song Liu wrote:
    > >> It is useful to trace functions in kernel/event/core.c. Allow ftrace for
    > >> them by removing $(CC_FLAGS_FTRACE) from Makefile.
    > >
    > > Did you try using the ftrace event with perf with this on?
    >
    > I have tried a few things, like
    >
    > perf stat -e probe:perf_read -I 1000
    > perf record -e probe:__x64_sys_perf_event_open -aR
    >
    > They all work fine.

    Did you try using perf with function-tracer or function-graph tracer?
    If you just want to trace those functions with kprobes, you can
    build your kernel with CONFIG_KPROBE_EVENTS_ON_NOTRACE=y, which allows
    you to probe perf_read etc.

    Thank you,


    --
    Masami Hiramatsu <mhiramat@kernel.org>

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