[Bug 51367] New: Major dwrite:analyzer, dwrite:layout and dwrite:font slowdown when adding (CJK) fonts

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=51367

Bug ID: 51367
           Summary: Major dwrite:analyzer, dwrite:layout and dwrite:font
                    slowdown when adding (CJK) fonts
           Product: Wine
           Version: 6.10
          Hardware: x86-64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: dwrite
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 70223
  --> https://bugs.winehq.org/attachment.cgi?id=70223
Command and fonts for Debian's locales

Adding fonts causes major slowdowns in dwrite:analyzer, dwrite:layout and
dwrite:font when running in Wine. On my test VM I get the following run times:

Base   Full set
dwrite:analyzer   <1s    50s
dwrite:layout     ~1s    46s
dwrite:font       ~2s    85s

On the TestBot's debiant2 VM dwrite:font actually runs in about 118 seconds
with the full set of fonts; which is why it times out about 6% of the time:

https://test.winehq.org/data/patterns.html#dwrite:font

The base set of font packages is:
  fonts-dejavu-core
  fonts-freefont-ttf
  fonts-liberation
  fonts-quicksand

The problem is that the base set produces unreadable text when running in a
Chinese, Japanese or Korean locale: all translated strings are replaced with a
set of black squares (surprisingly ar_MA, he_IL, hi_HI are ok). That does not
seem to impact the test results but it does not feel right either. At a minimum
if Debian says a given set of fonts are needed for a locale we should test the
said locale with that set of fonts.

So the full set of fonts was created by installing the font packages for all of
Debian's locale task packages and this is what debiant2 has. See
apt_wine_locales() in wt-install-dev [1]. For reference I attached the
corresponding set of packages.

The run time increase is not concentrated in one specific test_xxx() function
that would iterate over all the fonts. All test_xxx() functions take longer to
run. Even the test_CreateFontFromLOGFONT() run time increased to ~17s (iirc).
Yet it does not look like it's doing all that much.

To speed things up I modified dwrite:font to use multiple threads using the
same approach as d3d10core:d3d10core. However even with 8 threads that only
gained about 4 seconds out of 118s: each individual test function just took
longer.

Is that because of lots of global locking?
Or because each test adds/removes fonts forcing all the other threads to do
many rescans?
Are all fonts reloaded and analyzed despite most fonts not having changed?

[1] https://github.com/fgouget/wt-daily/blob/master/wt-install-dev#L556