linux-kernel - Re: [PATCH 00/13] perf_events: add support for sampling taken branches (v3)

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Message-ID: <4F22EAFD.1020006@fb.com>
Date:	Fri, 27 Jan 2012 10:20:45 -0800
From:	Arun Sharma <asharma@...com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Stephane Eranian <eranian@...gle.com>,
	<linux-kernel@...r.kernel.org>, <mingo@...e.hu>,
	<acme@...radead.org>, <robert.richter@....com>,
	<ming.m.lin@...el.com>, <andi@...stfloor.org>, <ravitillo@....gov>,
	<vweaver1@...s.utk.edu>
Subject: Re: [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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