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