Re: [Qemu-devel] [PATCH v2 6/6] nbd: use generic trace subsystem instead of TRACE macro

[Eric Blake]

On 06/29/2017 03:12 PM, Eric Blake wrote:
> On 06/21/2017 10:34 AM, Vladimir Sementsov-Ogievskiy wrote:
>> Starting from this patch to enable traces use -trace option of qemu or
>> -T, --trace option of qemu-img, qemu-io and qemu-nbd. For qemu traces
>> also can be managed by qmp commands trace-event-{get,set}-state.
> 
> Maybe:
> 
> Let NBD use the trace mechanisms already present in qemu. Now you can
> use the -trace optino of qemu, or the -T/--trace option of qemu-img,
> qemu-io, and qemu-nbd, to select nbd traces.  For qemu, the QMP commands
> trace-event-{get,set}-state can also toggle tracing on the fly.
> 
> I also mentioned in v1 that an actual command line example might be
> helpful (for example, is it qemu-nbd --trace "nbd_*" to get ALL nbd
> traces enabled?)

Answering myself: almost.  Either you have to use the pattern --trace
"*nbd_*", or better, you follow Paolo's advice to rename any 'do_nbd_'
traces to be just 'nbd_'.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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