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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