linux-kernel - Re: [PATCH v5] arm64: perf: Fix callchain parse error with kernel tracepoint events

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Date:	Wed, 20 May 2015 08:53:07 +0200
From:	Jean Pihet <jean.pihet@...oldbits.com>
To:	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>
Cc:	Hou Pengyang <houpengyang@...wei.com>, wangnan0@...wei.com,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>, acme@...nel.org,
	mingo@...hat.com, Paul Mackerras <paulus@...ba.org>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v5] arm64: perf: Fix callchain parse error with kernel
 tracepoint events

Hi Catalin, Will,

On Tue, May 19, 2015 at 6:52 PM, Catalin Marinas
<catalin.marinas@....com> wrote:
> On Sun, May 10, 2015 at 11:07:40AM +0000, Hou Pengyang wrote:
>> For ARM64, when tracing with tracepoint events, the IP and pstate are set
>> to 0, preventing the perf code parsing the callchain and resolving the
>> symbols correctly.
>>
>>  ./perf record -e sched:sched_switch -g --call-graph dwarf ls
>>     [ perf record: Captured and wrote 0.146 MB perf.data ]
>>  ./perf report -f
>>     Samples: 194  of event 'sched:sched_switch', Event count (approx.): 194
>>     Children      Self    Command  Shared Object     Symbol
>>     100.00%       100.00%  ls       [unknown]         [.] 0000000000000000
>>
>> The fix is to implement perf_arch_fetch_caller_regs for ARM64, which fills
>> several necessary registers used for callchain unwinding, including pc,sp,
>> fp and spsr .
>>
>> With this patch, callchain can be parsed correctly as follows:
>>
>>      ......
>> +    2.63%     0.00%  ls       [kernel.kallsyms]  [k] vfs_symlink
>> +    2.63%     0.00%  ls       [kernel.kallsyms]  [k] follow_down
>> +    2.63%     0.00%  ls       [kernel.kallsyms]  [k] pfkey_get
>> +    2.63%     0.00%  ls       [kernel.kallsyms]  [k] do_execveat_common.isra.33
>> -    2.63%     0.00%  ls       [kernel.kallsyms]  [k] pfkey_send_policy_notify
>>      pfkey_send_policy_notify
>>      pfkey_get
>>      v9fs_vfs_rename
>>      page_follow_link_light
>>      link_path_walk
>>      el0_svc_naked
>>     .......
>>
>> Signed-off-by: Hou Pengyang <houpengyang@...wei.com>
>> Acked-by: Will Deacon <will.deacon@....com>
>
> Queued for 4.2. Thanks.

Nice to see this one going out, finally.

Cheers,
Jean

>
> --
> Catalin
>
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> linux-arm-kernel@...ts.infradead.org
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