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Re: [Qemu-devel] [PATCH] trace: Trace SCSI request lifecycle


From: Blue Swirl
Subject: Re: [Qemu-devel] [PATCH] trace: Trace SCSI request lifecycle
Date: Tue, 9 Nov 2010 17:47:24 +0000

On Mon, Nov 8, 2010 at 9:30 PM, Stefan Hajnoczi <address@hidden> wrote:
> On Mon, Nov 8, 2010 at 7:18 PM, Blue Swirl <address@hidden> wrote:
>> On Mon, Nov 8, 2010 at 9:44 AM, Stefan Hajnoczi
>> <address@hidden> wrote:
>>> This patch adds trace events for SCSI request allocation, freeing, CDB
>>> parsing, read, and write.  These trace events can be used to instrument
>>> the SCSI request lifecycle.
>>
>> How about converting also the DPRINTFs in hw/scsi-disk.c to tracepoints?
>
> Good idea.  I don't understand the SCSI emulation well enough to trace
> 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.



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