linux-kernel - Re: [PATCH 3/5] perf core: Prepare writing into ring buffer from end

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Message-ID: <56F363A6.2010603@huawei.com>
Date:	Thu, 24 Mar 2016 11:48:54 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:	Peter Zijlstra <peterz@...radead.org>, <mingo@...hat.com>,
	<linux-kernel@...r.kernel.org>, He Kuang <hekuang@...wei.com>,
	"Alexei Starovoitov" <ast@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Zefan Li <lizefan@...wei.com>, <pi3orama@....com>
Subject: Re: [PATCH 3/5] perf core: Prepare writing into ring buffer from end



On 2016/3/24 3:25, Alexei Starovoitov wrote:
> On Wed, Mar 23, 2016 at 06:08:41PM +0800, Wangnan (F) wrote:
>>
>> On 2016/3/23 17:50, Peter Zijlstra wrote:
>>> On Mon, Mar 14, 2016 at 09:59:43AM +0000, Wang Nan wrote:
>>>> Convert perf_output_begin to __perf_output_begin and make the later
>>>> function able to write records from the end of the ring buffer.
>>>> Following commits will utilize the 'backward' flag.
>>>>
>>>> This patch doesn't introduce any extra performance overhead since we
>>>> use always_inline.
>>> So while I agree that with __always_inline and constant propagation we
>>> _should_ end up with the same code, we have:
>>>
>>> $ size defconfig-build/kernel/events/ring_buffer.o.{pre,post}
>>>     text    data     bss     dec     hex filename
>>>     3785       2       0    3787     ecb defconfig-build/kernel/events/ring_buffer.o.pre
>>>     3673       2       0    3675     e5b defconfig-build/kernel/events/ring_buffer.o.post
>>>
>>> The patch actually makes the file shrink.
>>>
>>> So I think we still want to have some actual performance numbers.
>> There are some numbers. You can find them from:
>>
>> http://lkml.iu.edu/hypermail/linux/kernel/1601.2/03966.html
> Wang, when you respin, please add all perf analysis that you've
> done and the reasons to do it this way to commit log
> to make sure it stays in git history.
>
> I've reviewed it in the past and looks like the patches didn't
> change over the last months. So still ack, I believe
> overwrite buffers is a great feature.
Can I add your Acked-by in all these 5 patches?

Thank you.