1391314 - reduce logging codesize by commoning LogModule conversions

Status: RESOLVED FIXED

(Core :: XPCOM, enhancement)

Description

[Nathan Froyd [:froydnj]]

The current definition of MOZ_LOG requires calling
LazyLogModule::operator() multiple times, which is unnecessary.  We can
avoid that with a bit of clever macro definition and a lengthy
explanation.

Comment 1

[Nathan Froyd [:froydnj]]

Attachment: reduce logging codesize by commoning LogModule conversions

The comment in Logging.h ideally tells you everything you need to know.

This reduces codesize by ~150K on Linux x86-64, but that measurement is on top
of bug 1386918, which I haven't yet gotten all the performance measurements
done on.  I think that means it should be even more effective without the other
bug's patch, but it would also decrease the impact of the other patch.

This patch's performance impact should be minimal to nonexistent,
unlike the other patch, since we had to call LazyLogModule::operator()
*anyway*; we're just making sure that the actual printing of the log message
doesn't have to call it again.

Comment 2

[Eric Rahm [:erahm]]

Comment on attachment 8898377 [details] [diff] [review]
reduce logging codesize by commoning LogModule conversions

Review of attachment 8898377 [details] [diff] [review]:
-----------------------------------------------------------------

Whoa! Nice find, r=me.

::: xpcom/base/Logging.h
@@ +199,5 @@
>  //     ...compute things to log and log them...
>  //   }
>  //
>  // This also has the nice property that no special definition of MOZ_LOG is
>  // required when logging is disabled.

I guess this isn't true anymore...

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/770ed08655c3
reduce logging codesize by commoning LogModule conversions; r=erahm

Comment 4

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/770ed08655c3