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From: Namhyung Kim <>
Subject: Re: [PATCH] block: add missing block_bio_complete() tracepoint
Date: Mon, 30 Jan 2012 10:44:19 +0900	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>


2012-01-30 4:24 AM, Tejun Heo wrote:
> On Sun, Jan 29, 2012 at 06:41:33 PM +0900, Namhyung Kim wrote:
>> The block_bio_complete() TP has been missed so long, so that bio-based
>> drivers haven't been able to trace its IO behavior. Add it.
>> In some rare cases, such as loop_switch, @bio->bi_bdev can be NULL.
>> Thus convert it to TRACE_EVENT_CONDITION() as Steven suggested.
>>  From now on, request-based drivers will also get BLK_TA_COMPLETEs for
>> all bio's in requests. This needs to be handled in userland properly.
>> Also remove external use of the TP in DM and unexport it.
>> Signed-off-by: Namhyung Kim <>
>> Cc: Tejun Heo <>
>> Cc: Steven Rostedt <>
>> Cc:
> I like the smiplicity change but do we know how we can filter this out
> from userland?  Also, what's the reason not to do it from blktrace.c?
> What would be the downside of doing that?
> Thanks.

The userland tool cannot distinguish bounced bio from original one at 
completion TP, but it can expect there will be a duplicated 
BLK_TA_COMPLETE as it sees BLK_TA_BOUNCE for the bio before.

Filtering it out from kernel side seems to hide a real information that 
(paranoid?) user might want to get, and it looks like providing "polcy 
not mechanism" IMHO. That's why I changed my mind finally.

I cannot think of the downside, anyway it's not a big deal, if you think 
it's wrong choice, I'm OK to change it again.


  reply	other threads:[~2012-01-30  1:44 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-29  9:41 [PATCH] block: add missing block_bio_complete() tracepoint Namhyung Kim
2012-01-29 19:24 ` Tejun Heo
2012-01-30  1:44   ` Namhyung Kim [this message]
2012-01-30  1:47     ` Tejun Heo
2012-01-30  2:22       ` Namhyung Kim
2012-01-30  2:30         ` Tejun Heo
2012-01-30  2:49           ` Namhyung Kim
2012-01-30  2:53             ` Tejun Heo
2012-01-30  5:51               ` Namhyung Kim
2012-01-30  5:54                 ` Tejun Heo
2012-01-30  6:02                   ` Namhyung Kim
2012-01-30  6:38 ` Namhyung Kim
2012-01-30 17:05   ` Tejun Heo
2012-01-31  6:30     ` Namhyung Kim
2012-01-31 10:39       ` Tejun Heo
2012-02-01  2:18         ` Namhyung Kim

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