266071 - slight perf loss after splitting libxpcom.so

Status: RESOLVED WONTFIX

(Core :: XPCOM, defect)

Description

[Darin Fisher]

slight perf loss after splitting libxpcom.so

the patch for bug 262218 seems to have degraded performance on linux slightly. 
Tp, Tdhtml, Txul and Ts were all affected.  however, win32 and osx platforms
appear to have been unaffected.

it's unclear how the library change could have impacted performance since we
just moved a library dependency from libxpcom.so to libxpcom_core.so.

a couple interesting points:

- previously, all components most likely accessed the copy of the string library
contained in mozilla-bin.  now, they are accessing it from libxpcom_core.so.

- all of our component libs now link to libxpcom_core.so as well as libxpcom.so,
even though they do not (or should not) be referencing any symbols in
libxpcom.so.  perhaps this is playing a role somehow.

Comment 1

[Darin Fisher]

might be worth it to try making mozilla-bin not dlopen libxpcom.so (i.e., skip
the pointless GRE dance).

Comment 2

[Darin Fisher]

Attachment: test patch

I applied this test patch to the trunk to see what it would do.  Here are some
early results:

btek Tp     : unaffected
luna Tp     : unaffected
luna Tdhtml : reduced by 30ms (out of a 40ms overall increase)
luna Txul   : reduced by 20ms (out of a 20ms overall increase)
luna Ts     : reduced by 50ms (out of a 100ms overall increase)

so, this doesn't really solve the mystery, but it certainly helps.

Comment 3

[Darin Fisher]

Comment on attachment 163525 [details] [diff] [review]
test patch

I'd like to leave this in since it helps a bit... so reviews seem to be in
order.

Comment 4

[Darin Fisher]

marking WONTFIX.  with libxul on the horizon, libxpcom_core shouldn't be around
long enough for us to care about this slight perf regression.