938221 - regression in windows 7 xperf mainthread bytes read during test run

Status: RESOLVED WORKSFORME

(Core :: Audio/Video, defect)

Description

[Joel Maher ( :jmaher ) (UTC -8)]

I saw this on dev.tree-management:
https://groups.google.com/forum/#!topic/mozilla.dev.tree-management/-IcVLGiEH54

it indicates we have a 3.56% increase in our bytes referenced.  This has been a fairly stable number for a long time. 

I looked at the main differences here and I see:
build filename                                               readcnt  readbytes
new   C:\slave\test\build\application\firefox\gkmedias.dll	156	10223616
orig  C:\slave\test\build\application\firefox\gkmedias.dll	110	 7208960	

This is a difference of:
3014656 bytes

The question is: are we expecting to see a couple MB of file IO from gkmedias.dll as a result of the patch in bug 931060?  Is this necessary?

Comment 1

[Ralph Giles (:rillian)]

The code added in bug 931060 isn't called from anywhere, so I wouldn't expect any additional IO. Is this runtime i/o executed by gkmedias.dll, or i/o related to accessing the dll itself?

It does add some large tables to the binary size; there's bug 937455 for slimming that.

Comment 2

[Vladan Djeric (:vladan)]

gkmedias.dll is being read in its entirety during startup, same as the other DLLs listed in dependentlibs.list file. Ehsan suggested we could move the parts of gkmedias.dll needed during most startups into xul.dll, and then skip preloading the remaining code in gkmedias.dll

There's currently no regression in ts_paint but that's cause gkmedias.dll is in the disk cache during the "warm" ts_paint startups. There would be a startup time regression if there was a Talos test to measure "cold" starts (bug 936617).

Comment 3

[(no longer active)]

Note that we need to make sure that putting those libraries back into libxul won't bring us too close to the PGO memory limit.

Comment 4

[Joel Maher ( :jmaher ) (UTC -8)]

Looking at the trend here:
http://graphs.mozilla.org/graph.html#tests=[[242,131,25]]&sel=none&displayrange=365&datatype=running

We have reduced our startup file i/o since this.  Please reopen if you feel there is something I have overlooked.