[Fontconfig-bugs] [Bug 94427] Performance regression in git compared 2.11

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94427

--- Comment #7 from ebiggers3 at gmail.com ---
I have been encountering this bug after upgrading from fontconfig 2.11.1-2 to
fontconfig 2.11.94-1 yesterday.

I can confirm the previous post that places the blame on the following commit:

commit f44bfad235e63bb792c38e16ae1fbd281ec1453b
Author: Akira TAGOH <akira at tagoh.org>
Date:   Thu Jun 5 19:06:02 2014 +0900

    Workaround another race condition issue

    See https://bugzilla.redhat.com/show_bug.cgi?id=921706

Also, the main reason for the performance regression is not the stat() calls
per se, but rather the inefficient "string sets" which take n^2 time to build,
causing millions of string comparisons to occur when any application is
started.  See FcStrSetMember(), called by _FcStrSetAppend().

Still, the entire "directory scan" seems unnecessary to me.  I don't yet fully
understand what problem this change was meant to solve, but in my opinion it's
not acceptable to iterate through all font files.  The purpose of the
fontconfig cache is to make that unnecessary, is it not?

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