Re: [Qemu-devel] [RFC][PATCH v3 03/21] virtproxy: add debug functions for virtproxy core

[Stefan Hajnoczi]

On Thu, Nov 18, 2010 at 5:17 PM, Michael Roth <address@hidden> wrote:
> On 11/18/2010 05:43 AM, Stefan Hajnoczi wrote:
>>
>> On Thu, Nov 18, 2010 at 11:09 AM, Jes Sorensen<address@hidden>
>>  wrote:
>>>
>>> On 11/16/10 02:15, Michael Roth wrote:
>>>>
>>>> Signed-off-by: Michael Roth<address@hidden>
>>>> ---
>>>>  virtproxy.c |   17 +++++++++++++++++
>>>>  1 files changed, 17 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/virtproxy.c b/virtproxy.c
>>>> index 8f18d83..3686c77 100644
>>>> --- a/virtproxy.c
>>>> +++ b/virtproxy.c
>>>> @@ -13,6 +13,23 @@
>>>>
>>>>  #include "virtproxy.h"
>>>>
>>>> +#define DEBUG_VP
>>>> +
>>>> +#ifdef DEBUG_VP
>>>> +#define TRACE(msg, ...) do { \
>>>> +    fprintf(stderr, "%s:%s():L%d: " msg "\n", \
>>>> +            __FILE__, __FUNCTION__, __LINE__, ## __VA_ARGS__); \
>>>> +} while(0)
>>>> +#else
>>>> +#define TRACE(msg, ...) \
>>>> +    do { } while (0)
>>>> +#endif
>>>> +
>>>> +#define LOG(msg, ...) do { \
>>>> +    fprintf(stderr, "%s:%s(): " msg "\n", \
>>>> +            __FILE__, __FUNCTION__, ## __VA_ARGS__); \
>>>> +} while(0)
>>>> +
>>>
>>> I wonder if it wouldn't make sense to do this in a more generic way and
>>> stick it in a header file. This type of debug code seems to show up
>>> repeatedly all over the place.
>>
>> I wanted to suggest actually using QEMU tracing but given that this
>> code compiles stand-alone, it may be more trouble to integrate than
>> it's worth.
>>
>> For qemu and qemu-tools code we should be using tracing because you
>> can build it into production without high overhead.  How often do
>> these #defines get used, not often is my guess because no one wants to
>> tweak the source and rebuild, especially not in production.
>>
>
> I'd planned on replacing the TRACE()'s with trace calls eventually. Maybe I
> missed it in the documentation, but do we have a way to enable them for
> qemu-tools or does we need to provide our own hooks and do it
> programmatically?

qemu-tools builds with QEMU tracing.  I wasn't sure whether you're
building in the qemu-tools style or whether qemu-vp is a completely
separate program.

So if qemu-vp is built with all the common qemu-tools make
infrastructure, then you should have tracing in there.

Stefan