[cairo] fixing Cairo's FreeType multi-threaded usage

[David Turner]

I can reproduce the problem with your test, I've just started investigating.
will post later with conclusion and, I hope, a fix

thanks a lot,

- David

On Sat, 3 Mar 2007 04:23:33 +0100 (CET), "Jan Slupski" <jslupski at juljas.net> said:
> On Sat, 3 Mar 2007, David Turner wrote:
> 
> > no, this is not normal at all; I'm running my desktop on this patch and
> > haven't seen any regression in performance. Are you sure your merge happened
> > without conflicts ?
> 
> No, no conflicts. Only few 'fuzz'.
> 
> Except makefiles these are:
> 
> $ bzcat ../fix-freetype-usage-1.patchset.bz2 | patch -p1
> (...)
> patching file src/cairo-debug.c
> Hunk #1 succeeded at 66 with fuzz 2.
> (...)
> patching file src/cairoint.h
> Hunk #1 succeeded at 623 (offset 4 lines).
> Hunk #3 succeeded at 1214 (offset 2 lines).
> 
> Should I try any earlier cairo snapshot?
> 
> > the long story is that some of the intermediate commits in the patchset do
> > produce correct behaviour and very poor performance, but this is normally
> > fixed in later ones.
> >
> > In the event your merge didn't work correctly, you could be left in one of
> > these hideously slow cases. I've just checked the patchset file, and the
> > changes described there seem ok.
> >
> > Could you give more details about your test cases ? it may be interesting.
> 
> Seems that I am able to reproduce these on my simple cairo threads test
> case
> I used before to hunt previous problems. (attached)
> 
> Cairo-git:
> real    0m2.551s
> user    0m2.530s
> sys     0m0.020s
> 
> Cairo-git + fix-freetype-usage-1.patchset:
> real    0m12.956s
> user    0m12.950s
> sys     0m0.010s
> 
> Command used: time ./threads 1 10000 
> (one thread, 10K loops)
> 
> 
> Before I used two samples (against some external library that calls
> cairo) on two Linux machines. Slowdown with patch applied was:
> - between 2x (x86_64 dual) and 6x (i386) - first sample
> - between 6x (x86_64 dual) and 60x+ (i386) really! - another sample
> 
> I'm sure about these results, but if you find them unbelivable
> and cannot reproduce, I'll repeat tests from scratch to make it 200%
> sure...
> 
> 
> Thanks a lot,
> Jan
> 
> 
> 
> > On Sat, 3 Mar 2007 01:47:49 +0100 (CET), "Jan Slupski" <jslupski at juljas.net> said:
> >> On Wed, 28 Feb 2007, David Turner wrote:
> >>
> >>> Hello,
> >>>
> >>> here's the first version of my patches to fix Cairo's usage of FreeType with multiple
> >>> threads. It's rather big, so I'll summarize things here a little:
> >>
> >> Hi David,
> >>
> >> I tried your patches against the current git cairo (latest commit
> >> fed13e77e1de071ddaaf829aced10b02f6bc8c90).
> >>
> >> Is it expected that cairo with these patches runs *much* slower
> >> than without? I'm running simple test case and it seems to be
> >> 8+ times slower even in single thread.
> >>
> >> Is there anything special I should do (i.e. revert some already
> >> merged patches)?
> >>
> >> I'll try to figure out what exactly caused the slowdown, but any hints
> >> are apperciated...
> >>
> >> I have used default setup (./autogen.sh; make) and
> >> fontconfig 2.4.2, freetype 2.1.7 & 2.3.1
> 
>     _  _  _  _  _____________________________________________
>     | |_| |\ |  S L U P S K I             jslupski at juljas.net
>   |_| | | | \|                             http://juljas.net/