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

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Message-ID: <20150519165202.GA21251@e104818-lin.cambridge.arm.com>
Date:	Tue, 19 May 2015 17:52:03 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Hou Pengyang <houpengyang@...wei.com>
Cc:	will.deacon@....com, wangnan0@...wei.com, a.p.zijlstra@...llo.nl,
	linux-kernel@...r.kernel.org, acme@...nel.org, mingo@...hat.com,
	paulus@...ba.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5] arm64: perf: Fix callchain parse error with kernel
 tracepoint events

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.

-- 
Catalin
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