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Subject: Re: [PATCH 09/17] perf tools: Detect avalibility of write_backward
To: Arnaldo Carvalho de Melo <acme@kernel.org>
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CC: <arnaldo.melo@gmail.com>, <linux-kernel@vger.kernel.org>,
        He Kuang <hekuang@huawei.com>,
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        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
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From: "Wangnan (F)" <wangnan0@huawei.com>
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Date: Fri, 20 May 2016 23:31:44 +0800
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On 2016/5/13 21:08, Arnaldo Carvalho de Melo wrote:
> Em Fri, May 13, 2016 at 07:56:06AM +0000, Wang Nan escreveu:
>> Detect avalibility of write_backward and save the result into
>> record_opts. With write_backward the start pointer of a ring
>> buffer mapped read only can be found reliably.
> We have perf_missing_features for that, please try to use it.

I'll try it, but write_backward can't fallback, if kernel doesn't
support it, I think we'd better throw an error earlier. Using
perf_missing_features we get error during opening the event, so if we want
to fail earlier we still need API probing.

Thank you.