Bringing this thread up again, is it really true to say that
if (trace) log.trace("blah")
is as cheap as
log.trace("blah")
?
In the former, with tracing disabled, nothing happens after the condition check. In the
latter, you still construct a String "blah", and even if there is no complex
interpolation or message construction, the basic String message is still constructed (and
starts to take up PermGen space too, as literals are interned [1]).
So the case for the if (trace) pattern still stands IMO.
Cheers
Manik
[1]
http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/String.html#intern()
"All literal strings and string-valued constant expressions are interned."
On 28 Sep 2011, at 17:41, David M. Lloyd wrote:
On 09/28/2011 11:35 AM, Mircea Markus wrote:
> Hi,
>
> I'm not aware of any convention on using trace vs log.isTraceEnabled() to guard
the trace statements.
>
> if (trace) log.trace("some request related stuff")
> vs
> if (log.isTraceEnabled()) log.trace("some request related stuff");
>
> The former is more efficient, but cannot be managed at runtime. It seems to be the
preferred form, so shall we stick with it?
If you're using the jboss-logging API, and your log statement does not
do any interpolation, then it is just as fast to do any of the following
(with no if):
log.trace("blah");
log.tracef("the %s happened to %s", foo, bar);
log.tracev("the {0} happened to {1}", foo, bar);
In the case where trace logging is disabled, these are exactly as
efficient as the if (log.isTraceEnabled()) variants. In the case where
it is enabled, it is marginally more efficient (though the trace log
itself is substantially more expensive of course).
Overall I'd avoid the "if" forms unless you're doing complex
interpolation:
log.trace("Foo " + bar + " baz " + zap);
log.tracef("the %s happened to %s", fooMethod().barMethod(), bar);
...both of which incur the expense of the expression resolution even if
the log message is ultimately discarded.
--
- DML
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Manik Surtani
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Lead, Infinispan
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