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Date: Tue, 19 Jan 2016 18:20:21 -0800
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Wangnan (F)" <wangnan0@huawei.com>
Cc: peterz@infradead.org, ast@kernel.org, linux-kernel@vger.kernel.org,
        He Kuang <hekuang@huawei.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
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        Jiri Olsa <jolsa@kernel.org>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Namhyung Kim <namhyung@kernel.org>, Zefan Li <lizefan@huawei.com>,
        pi3orama@163.com
Subject: Re: [PATCH 0/6] perf core: Read from overwrite ring buffer
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On Wed, Jan 20, 2016 at 09:37:42AM +0800, Wangnan (F) wrote:
> 
> 
> On 2016/1/20 1:42, Alexei Starovoitov wrote:
> >On Tue, Jan 19, 2016 at 11:16:44AM +0000, Wang Nan wrote:
> >>This patchset introduces two methods to support reading from overwrite.
> >>
> >>  1) Tailsize: write the size of an event at the end of it
> >>  2) Backward writing: write the ring buffer from the end of it to the
> >>     beginning.
> >what happend with your other idea of moving the whole header to the end?
> >That felt better than either of these options.
> 
> I'll try it today. However, putting all of the three together is
> not as easy as this patchset.

I'm missing something. Why all three in one set?
Since you have 1 and 2 implemented, benchmark them with absolute
numbers and then implement this last one without any prior baggage
and benchmark it as well. I think it should be the fastest
and the cleanest. We don't need ten different ways to do one thing.