[dtrace-discuss] self-> in BEGIN probe

[Robert Milkowski]

Hello Menno,

Wednesday, February 14, 2007, 11:30:16 AM, you wrote:


ML> ----- Original Message -----
ML> From: Robert Milkowski <rmilkowski at task.gda.pl>
ML> Date: Wednesday, February 14, 2007 11:02 am
ML> Subject: [dtrace-discuss] self-> in BEGIN probe
ML> To: dtrace-discuss at opensolaris.org

>> Hello dtrace-discuss,
>> 
>> 
>> With a bug id
>> 
>> 6495013 Loops and recursion in metaslab_ff_alloc can kill
>>        performance, even on a pool with lots of free data
>> 
>> There's associated D script below.
>> 
>> What's the point setting self->in_metaslab in a BEGIN probe?
>> I'm not talking about setting it to 0 as this is not necessary but
>> rather about self-> variables in BEGIN probe. I guess it has no
>> rather about self-> predictable meaning, right?
>> 

ML> I think it is used as a forward declaration. The predicate on the
ML> first clause would cause the script not to run since
ML> slef->in_metaslab would be undefined at that point. The proper way
ML> to do the forward declaration would be something like:

Actually it will work without declaration on BEGIN only you are
checking for zero (or non zero).


ML> #!/usr/sbin/dtrace -s

ML> #pragma D option quiet

ML> self int in_metaslab;

That's interesting - I didn't know one can do it for self-> variables
in that way.



-- 
Best regards,
 Robert                            mailto:rmilkowski at task.gda.pl
                                       http://milek.blogspot.com