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From: Blue Swirl <blauwirbel@gmail.com>
Date: Tue, 9 Nov 2010 17:47:24 +0000
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Subject: Re: [Qemu-devel] [PATCH] trace: Trace SCSI request lifecycle
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, qemu-devel@nongnu.org

On Mon, Nov 8, 2010 at 9:30 PM, Stefan Hajnoczi <stefanha@gmail.com> wrote:
> On Mon, Nov 8, 2010 at 7:18 PM, Blue Swirl <blauwirbel@gmail.com> wrote:
>> On Mon, Nov 8, 2010 at 9:44 AM, Stefan Hajnoczi
>> <stefanha@linux.vnet.ibm.com> wrote:
>>> This patch adds trace events for SCSI request allocation, freeing, CDB
>>> parsing, read, and write. =C2=A0These trace events can be used to instr=
ument
>>> the SCSI request lifecycle.
>>
>> How about converting also the DPRINTFs in hw/scsi-disk.c to tracepoints?
>
> Good idea. =C2=A0I don't understand the SCSI emulation well enough to tra=
ce
> the rest, so I couldn't do much besides a mechanical conversion.

I also did only a mechanical conversion of Sparc32 devices earlier. I
thought about removing or merging some of them, but then I considered
that more tracepoints may be better to fewer. Is there a downside?

There's a difference in the viewpoints. DPRINTFs may have been
designed with debugging internal logic in mind. Alternatively we could
be interested in only tracing the external interfaces. I don't think
these views are in conflict since tracepoints are much more precise
than DPRINTFs.