linux-kernel - Re: [PATCH RESEND 9/9] block, trace: implement ioblame

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Message-ID: <4F0E38E6.4070606@lge.com>
Date:	Thu, 12 Jan 2012 10:35:34 +0900
From:	Namhyung Kim <namhyung.kim@....com>
To:	Tejun Heo <tj@...nel.org>
CC:	Namhyung Kim <namhyung@...il.com>, axboe@...nel.dk,
	mingo@...hat.com, rostedt@...dmis.org, fweisbec@...il.com,
	teravest@...gle.com, slavapestov@...gle.com, ctalbott@...gle.com,
	dhsharp@...gle.com, linux-kernel@...r.kernel.org,
	winget@...gle.com, Chanho Park <chanho61.park@...sung.com>
Subject: Re: [PATCH RESEND 9/9] block, trace: implement ioblame - IO tracer
 with origin tracking

Hello,

2012-01-12 10:14 AM, Tejun Heo wrote:
> Hello,
>
> On Wed, Jan 11, 2012 at 5:05 PM, Namhyung Kim<namhyung.kim@....com>  wrote:
>> Yes. But that's a text-based so it might fit better to simple use cases. If
>> we need further post processing based on intents, it could be better off
>> having binary interface IMHO. And since we already use tracepoints anyway,
>> wouldn't it be good to avoid adding another layer of interface or
>> complexity?
>
> The thing is that all entries are needed for any post processing, not
> only the new ones. To use TP, either there needs to be special
> "trigger the TP for all existing entries" switch somewhere or
> ioblame/intents file needs to be read for existing entries. Even then,
> TPs aren't guaranteed to be reliable. There's no way to detect
> overflow and re-emit the event. It just isn't the right interface. The
> previous version had intents_bin file in binary format but given that
> there aren't too many of intents, binary interface didn't seem
> necessary and ripped it out. Adding it back isn't difficult at all but
> I'm not sure that's a good idea. It's not like parsing the intents
> file is difficult.
>
> Thanks.
>

Why do we need to trigger the TP for existing ones as we keep each entry 
at its creation? Maybe I'm missing something?

Thanks,
Namhyung Kim
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