From: Tejun Heo <tj@kernel.org>
To: Namhyung Kim <namhyung.kim@lge.com>
Cc: axboe@kernel.dk, mingo@redhat.com, rostedt@goodmis.org,
fweisbec@gmail.com, teravest@google.com, slavapestov@google.com,
ctalbott@google.com, dsharp@google.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 03/11] block: block_bio_complete tracepoint was missing
Date: Sun, 8 Jan 2012 17:49:49 -0800 [thread overview]
Message-ID: <20120109014949.GA16360@mtj.dyndns.org> (raw)
In-Reply-To: <4F0A431E.3090106@lge.com>
Hello,
On Mon, Jan 09, 2012 at 10:30:06AM +0900, Namhyung Kim wrote:
> Just adding the TP unconditionally will produce duplicated (in some
> sense) reports about the completion. For example, normal request
> based IO reports whole request completion prior to its bio's, and
> further
Request and bio completions are separate events. There's nothing
wrong with reporting them separately. In fact, I think they should be
reported separately.
>, some of nested block IO handling routines - bounced bio and
> btrfs with compression, etc - call bio_endio() more than once. Also
> there are cases that bio fails before it's enqueued for some reason.
They are actually separate bio's being completed. I don't think
trying to put extra semantics on TP itself is a good idea. In
general, TP signals that such event happened with sufficient
information and it's the consumers' responsibility to make sense of
what's going on. BIO_CLONED/BOUNCED are there.
> I have no idea about the ioblame can deal with all of such corner
> cases. However it might confuse blktrace somewhat, I guess.
Unless someone is doing memcpy() on bio's, ioblame should be okay. It
only considers bio's which went through actual submission.
> I already posted similar patch a couple of weeks ago, but didn't
> receive a comment yet. [1] Please take a look this too :)
I'll reply there but don't think imposing such extra logic on TP is a
good idea.
> After a quick glance, the ioblame seems to carry all IO accounting
> info through the first bio in the request. If so, why don't you use
> the request structure for that?
Because there are bio based drivers which don't use requests at all.
Thanks.
--
tejun
next prev parent reply other threads:[~2012-01-09 1:49 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-05 23:42 [RFC PATCHSET RESEND] ioblame: statistical IO analyzer Tejun Heo
2012-01-05 23:42 ` [PATCH 01/11] trace_event_filter: factorize filter creation Tejun Heo
2012-01-05 23:42 ` [PATCH 02/11] trace_event_filter: add trace_event_filter_*() interface Tejun Heo
2012-01-05 23:42 ` [PATCH 03/11] block: block_bio_complete tracepoint was missing Tejun Heo
2012-01-09 1:30 ` Namhyung Kim
2012-01-09 1:49 ` Tejun Heo [this message]
2012-01-09 2:33 ` Namhyung Kim
2012-01-05 23:42 ` [PATCH 04/11] block: add @req to bio_{front|back}_merge tracepoints Tejun Heo
2012-01-05 23:42 ` [PATCH 05/11] block: abstract disk iteration into disk_iter Tejun Heo
2012-01-05 23:42 ` [PATCH 06/11] writeback: move struct wb_writeback_work to writeback.h Tejun Heo
2012-01-05 23:42 ` [PATCH 07/11] writeback: add more tracepoints Tejun Heo
2012-01-05 23:42 ` [PATCH 08/11] block: add block_touch_buffer tracepoint Tejun Heo
2012-01-05 23:42 ` [PATCH 09/11] vfs: add fcheck tracepoint Tejun Heo
2012-01-05 23:42 ` [PATCH 10/11] stacktrace: implement save_stack_trace_quick() Tejun Heo
2012-01-05 23:42 ` [PATCH 11/11] block, trace: implement ioblame IO statistical analyzer Tejun Heo
2012-01-06 9:00 ` [RFC PATCHSET RESEND] ioblame: statistical IO analyzer Namhyung Kim
2012-01-06 16:02 ` Tejun Heo
2012-01-06 16:33 ` Tejun Heo
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