Re: Review: DTrace probes (merged version)

Alvaro Herrera napsal(a):
> Zdenek Kotala wrote:
>> Tom Lane napsal(a):
> 
>>> I see no value in cluttering the system with useless probes.  The
worker
>>> start/stop are the only ones here with any conceivable application
IMHO.
>> As I answered to Alvaro. I needed to catch start of backend several
times 
>> to track call flow or attach debugger. It is possible to use some other

>> dtrace magic for that, but it is not easy and there is not way how to 
>> determine what kind of process it is.  For example how to measure how 
>> many writes performs bgwriter?
> 
> If you need to attach a debugger to a backend, you can use the -W switch
> (even on PGOPTIONS if you need it for a particular backend, AFAIR).  If
> you want to "truss" it I guess you can use -W too.
> 
> Does it have any usefulness beyond that?
> 

Why use million of tools when you can use one? And truss monitors only
syscalls 
but with dtrace you are able to use/trace over 80000 probes in the kernel,
libc 
and so on. I agree that for debugger you can use -W option but in
situation when 
you are not able to use this switch (e.g on customer production machine)
dtrace 
is only possible solution. That is why I think that this probes are
useful.


		Zdenek

-- 
Zdenek Kotala              Sun Microsystems
Prague, Czech Republic     http://sun.com/postgresql


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