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Date:	Mon, 01 Sep 2014 15:38:07 +0900
From:	Yoshihiro YUNOMAE <>
To:	Hannes Reinecke <>
	"Martin K. Petersen" <>,,,
	"James E.J. Bottomley" <>,
	Hidehiro Kawai <>,
	Doug Gilbert <>,
	Masami Hiramatsu <>,
	Christoph Hellwig <>
Subject: Re: [RFC PATCH 10/10] scsi/trace: Use scsi_print_command trace point
 instead of printk

Hi Hannes,

Sorry for the late reply.

(2014/08/28 21:15), Hannes Reinecke wrote:
> On 08/28/2014 08:19 AM, Yoshihiro YUNOMAE wrote:
>> Hi Hannes,
>> I tried to remove duplicated decoder of SCSI command, but the
>> output format of it in constants.c is different from it in traceevents.
>> I have two questions for it.
>> (Ex1)
>> traceevents: TEST_UNIT_READY
>> constants: Test Unit Ready
>> => Which of "XXX_YYY_ZZZ" and "Xxx Yyy Zzz" should the kernel output
>> strings? This difference comes from difference of implementation.
>> The decoder in traceevents are using macro. So, it cannot define
>> separated words. On the other hand, the decoder in constants are using
>> constant string array table. So, it can define separated words.
> I would go with the wording in constants.c, but set in double quotes
> like "Test Unit Ready" to avoid parsing errors later on.

OK, we use constants' format and add double quotes for each sense code.

>> (Ex2)
>> traceevents: (nothing)
>> constants: Set limits(12)
>> => Should we merge those decoder?
> Yes, I would prefer this. Again, we should be setting the strings in
> double quotes irrespective if there are spaces in the resulting string
> or not.


>> I understand we use the decoder of constants, but we need to solve
>> these problems. Would you give me your comments?
> As mentioned previously, my aim is to convert the logging system in
> several steps:
> a) convert all lone 'printk' statements into dev_printk() variants
>     and ensure everything is printed in one statement to avoid
>     linebreaks in the resulting logging message.
>     This will eliminate the immediate problem we're having, namely
>     that debugging is near to impossible under high load.
>     The patchset is nearing completion, and I will be posting it
>     later this week.
> b) Convert scsi_trace to use the functions from constants.c to
>     avoid code duplication and update scsi_trace to log sense codes.
> c) Remove all logging functions in the hot path (ie
>     SCSI_LOG_MLQUEUE and SCSI_LOG_MLCOMPLETE) and replace them
>     with trace events.
> b) is what you're working on, right?


> For 'c)' the problem is that we should retain the existing functionality
> with scsi_logging_level here, at least initially.
> So we cannot just replace it, as this would leave SCSI_LOG_ML
> a dummy without any real functionality.

I tried to change printk messages to new tracevents, but I'll stop it
until we solve the problem.
I'll submit the patch set removing duplicated decoder first.

Yoshihiro YUNOMAE

Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory

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