linux-kernel - Re: [PATCH] mmc: Provide tracepoints for request processing

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Message-ID: <CAMz4kuK-USLj5dcR+b3J_bvrjQBbprnoiOTfijFC0FLadhyP+w@mail.gmail.com>
Date:	Mon, 28 Mar 2016 12:55:05 +0800
From:	Baolin Wang <baolin.wang@...aro.org>
To:	Jens Axboe <axboe@...com>
Cc:	Ulf Hansson <ulf.hansson@...aro.org>,
	Steven Rostedt <rostedt@...dmis.org>, mingo@...hat.com,
	adrian.hunter@...el.com, yangbo.lu@...escale.com,
	akpm@...ux-foundation.org, JBottomley@...n.com, lporzio@...ron.com,
	jonathanh@...dia.com, Grant Grundler <grundler@...omium.org>,
	fabf@...net.be, yunpeng.gao@...el.com, dan.j.williams@...el.com,
	rabin.vincent@...s.com, chuanxiao.dong@...el.com,
	shawn.lin@...k-chips.com,
	Heiko Stübner <heiko@...ech.de>,
	Douglas Anderson <dianders@...omium.org>, david@...tonic.nl,
	Mark Brown <broonie@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Takahiro Akashi <takahiro.akashi@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-mmc@...r.kernel.org
Subject: Re: [PATCH] mmc: Provide tracepoints for request processing

On 25 March 2016 at 22:07, Jens Axboe <axboe@...com> wrote:
> On 03/25/2016 01:32 AM, Baolin Wang wrote:
>>
>> On 24 March 2016 at 22:08, Jens Axboe <axboe@...com> wrote:
>>>
>>> On 03/24/2016 05:54 AM, Baolin Wang wrote:
>>>>
>>>>
>>>> This patch provides some tracepoints for the lifecycle of a request from
>>>> fetching to completion to help with performance analysis of MMC
>>>> subsystem.
>>>
>>>
>>>
>>> Most of these already exist as block layer trace points, why do we need
>>> mmc
>>> specific ones?
>>
>>
>> Currently the MMC core does not have any tracepoints for use with
>> ftrace. These are very useful as they provide a very low overhead
>> runtime controllable way of getting diagnostics from the system which
>> is capable of recording a great deal of information without impacting
>> system performance. We have tracepoints in the block layer so we can
>> do some trace of MMC but none in MMC itself so adding some where
>> appropriate would help people follow the activity of subsystem.
>
>
> But more than half of the trace points you added, those are DIRECTLY related
> to the block event. So what you are saying makes little sense. I see you
> resend it with the same trace points, I'll comment on that mail.

OK. I'll address your comments on that new mail. Thanks.

>
> --
> Jens Axboe
>



-- 
Baolin.wang
Best Regards