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From: Ingo Molnar <mingo@kernel.org>
To: "Wangnan (F)" <wangnan0@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	David Ahern <dsahern@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Milian Wolff <milian.wolff@kdab.com>,
	linux-kernel@vger.kernel.org, pi3orama <pi3orama@163.com>,
	lizefan 00213767 <lizefan@huawei.com>
Subject: Re: [BUG REPORT] perf tools: x86_64: Broken calllchain when sampling taken at 'callq' instruction
Date: Thu, 19 Nov 2015 07:37:10 +0100	[thread overview]
Message-ID: <20151119063709.GA14852@gmail.com> (raw)
In-Reply-To: <564C3BAA.4040806@huawei.com>


* Wangnan (F) <wangnan0@huawei.com> wrote:

> >perf cmdline is
> >
> ># ./pref record  -g -F 9 --call-graph dwarf ./test_dwarf_unwind
> >
> >Use default events, precise_ip == 2 so uses PEBS.
> >
> 
> Testetd 'cycles', 'cycles:p' and 'cycles:pp'. Only 'cycles:pp' captures
> sample at callq. So maybe a PEBS problem?

Well, that's how our PEBS sampling works: we roll back the instruction pointer to 
point at the instruction generating the sample. The state itself is 
post-instruction.

So dwarf unwind has to take this into account. Should the kernel pass in the 
original (uncorrected) RIP as well, perhaps?

Thanks,

	Ingo

  reply	other threads:[~2015-11-19  6:37 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-18  7:20 [BUG REPORT] perf tools: x86_64: Broken calllchain when sampling taken at 'callq' instruction Wangnan (F)
2015-11-18  8:00 ` Wangnan (F)
2015-11-18  8:20   ` Ingo Molnar
2015-11-18  8:42     ` Wangnan (F)
2015-11-18  8:49       ` Wangnan (F)
2015-11-19  6:37         ` Ingo Molnar [this message]
2015-11-19  6:45           ` Wangnan (F)
2015-11-19 10:23             ` Ingo Molnar
2015-11-19 10:43               ` Wangnan (F)
2015-11-19 11:28                 ` Peter Zijlstra
2015-11-19 11:23               ` Peter Zijlstra
2015-11-27  8:38                 ` Ingo Molnar
2015-11-30  9:28                   ` Peter Zijlstra
2015-12-01  7:28                     ` Ingo Molnar
2015-12-01  8:38                       ` Peter Zijlstra
2015-12-01 16:11                         ` Ingo Molnar
2015-12-01 17:21                           ` Peter Zijlstra
2015-12-02  9:55                             ` Ingo Molnar
2015-11-18  8:48 ` Jiri Olsa
2015-11-18  9:02   ` Wangnan (F)

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