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    SubjectRe: [PATCH 00/13] perf_events: add support for sampling taken branches (v3)
    On 1/27/12 4:09 AM, Peter Zijlstra wrote:
    >> Here is a kernel example, where we want to sample indirect calls:
    >> $ perf record -a -C 1 -b ind_call -e r1c4:k sleep 10
    >> $ perf report -b
    >> #
    >> # Overhead Source Symbol Target Symbol
    >> # ........ .......................... ..........................
    >> #
    >> 36.36% [k] __delay [k] delay_tsc
    >> 9.09% [k] ktime_get [k] read_tsc
    >> 9.09% [k] getnstimeofday [k] read_tsc
    >> 9.09% [k] notifier_call_chain [k] tick_notify
    >> 4.55% [k] cpuidle_idle_call [k] intel_idle
    >> 4.55% [k] cpuidle_idle_call [k] menu_reflect
    >> 2.27% [k] handle_irq [k] handle_edge_irq
    >> 2.27% [k] ack_apic_edge [k] native_apic_mem_write
    >> 2.27% [k] hpet_interrupt_handler [k] hrtimer_interrupt
    >> 2.27% [k] __run_hrtimer [k] watchdog_timer_fn
    >> 2.27% [k] enqueue_task [k] enqueue_task_rt
    >> 2.27% [k] try_to_wake_up [k] select_task_rq_rt
    >> 2.27% [k] do_timer [k] read_tsc
    >>
    >> Due to HW limitations, branch filtering may be approximate on
    >> Core, Atom processors. It is more accurate on Nehalem, Westmere
    >> and best on Sandy Bridge.
    >
    > Can I have you ACK on this userspace stuff (patches 11-13)?

    While the current "Source -> Target" based UI works well for many cases,
    it'd be nice to have "-g -b any_call" to result in a callgraph like
    output, so for userspace programs compiled without frame pointers, we
    get a limited callgraph.

    -Arun


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