[Fontconfig] Application startup performance

[Behdad Esfahbod]

On 16-01-11 04:28 PM, Behdad Esfahbod wrote:
> On 16-01-11 03:30 PM, Keith Packard wrote:
>> Behdad Esfahbod <behdad.esfahbod at gmail.com> writes:
>>
>>> Humm.  I don't know when things changed, but as far as I understand, we
>>> readdir() every time; the cache just caches the patterns for each
>>> file.
>>
>> That's wrong -- fontconfig knows all of the directories in the hierarchy
>> and should be able to just stat each of them; if none of the existing
>> directories have changed, then no new fonts could have been added to the
>> system. Stat'ing a few known directories should suffice to track whether
>> the cache is up to date. And, it used to work this way, so something has
>> been broken.
> 
> Right.  Seems to be introduced by the never-ending series of "fix race
> condition" patches.  In particular:
> 
> 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

Akira,

Do you remember what the issue actually was?  Neither the commit log nor the
bug history really mention that!

b


> Here's the stacktrace:
> 
> #0  FcStat (file=0x626710 "/home/behdad/.fonts/ArabicSansBY-Regular.otf",
>     statb=statb at entry=0x7fffffffcd60) at fcstat.c:127
> #1  0x00007ffff7ba7e3f in IA__FcFileIsDir (file=<optimized out>) at fcdir.c:36
> #2  0x00007ffff7ba84a1 in FcDirScanConfig (set=0x0, dirs=0x625a80,
>     blanks=<optimized out>, dir=<optimized out>, force=<optimized out>,
>     config=0x603040, scanOnly=1) at fcdir.c:309
> #3  0x00007ffff7ba85c3 in FcDirScanOnly (dirs=dirs at entry=0x625a80,
>     dir=dir at entry=0x609390 "/home/behdad/.fonts",
>     config=config at entry=0x603040) at fcdir.c:348
> #4  0x00007ffff7b9f316 in FcCacheDirsValid (config=config at entry=0x603040,
>     cache=cache at entry=0x7ffff7f9d000) at fccache.c:604
> #5  0x00007ffff7b9fd1d in FcDirCacheMapFd (config=config at entry=0x603040,
>     fd=fd at entry=3, fd_stat=fd_stat at entry=0x7fffffffcf40,
>     dir_stat=dir_stat at entry=0x7fffffffcfd0) at fccache.c:684
> #6  0x00007ffff7b9fd69 in FcDirCacheMapHelper (config=config at entry=0x603040,
>     fd=fd at entry=3, fd_stat=fd_stat at entry=0x7fffffffcf40,
>     dir_stat=dir_stat at entry=0x7fffffffcfd0,
>     closure=closure at entry=0x7fffffffd0e8) at fccache.c:725
> #7  0x00007ffff7b9f788 in FcDirCacheProcess (config=config at entry=0x603040,
>     dir=<optimized out>,
>     callback=callback at entry=0x7ffff7b9fd60 <FcDirCacheMapHelper>,
>     closure=closure at entry=0x7fffffffd0e8,
>     cache_file_ret=cache_file_ret at entry=0x0) at fccache.c:224
> #8  0x00007ffff7b9feaa in IA__FcDirCacheLoad (dir=<optimized out>,
>     config=config at entry=0x603040, cache_file=cache_file at entry=0x0)
>     at fccache.c:738
> #9  0x00007ffff7ba88a2 in IA__FcDirCacheRead (
>     dir=dir at entry=0x607040 "/home/behdad/.fonts", force=force at entry=0,
>     config=config at entry=0x603040) at fcdir.c:477
> #10 0x00007ffff7ba3e9b in FcConfigAddDirList (config=config at entry=0x603040,
>     set=set at entry=FcSetSystem, dirSet=0x603150) at fccfg.c:380
> #11 0x00007ffff7ba3f4b in IA__FcConfigBuildFonts (
>     config=config at entry=0x603040) at fccfg.c:413
> #12 0x00007ffff7bad536 in FcInitLoadOwnConfigAndFonts (config=0x603040,
>     config at entry=0x0) at fcinit.c:163
> #13 0x00007ffff7bad567 in IA__FcInitLoadConfigAndFonts () at fcinit.c:174
> #14 0x00007ffff7ba16e7 in FcConfigEnsure () at fccfg.c:46
> 
> 
> The cache is due for a rewrite, though I have no idea where to start or who
> should do it.
> 
> b
> 

-- 
behdad
http://behdad.org/