[poppler] performance bottleneck of SplashFont cache.

[Sam Liao]

Hi All,

I tried to a perf analysis of the poppler library with the perf-test
program, and follwing result:

[kernel.kallsyms] with build id
ebfb885c6b5fc2a5bccbb13e06f9ff8b23596ee9 not found, continuing without
symbols
# Events: 2K cycles
#
# Overhead         Command         Shared Object
# ........  ..............  ....................
...............................................................................................................................................................
#
    30.27%       perf-test  libfreetype.so.6.6.2  [.] 0x5501d
            |
            --- _start
                __libc_start_main
                main
                PdfEnginePoppler::renderBitmap(int, double, int)
                PDFDoc::displayPage(OutputDev*, int, double, double,
int, bool, bool, bool, bool (*)(void*), void*, bool (*)(Annot*,
void*), void*)
                Page::display(OutputDev*, double, double, int, bool,
bool, bool, Catalog*, bool (*)(void*), void*, bool (*)(Annot*, void*),
void*)
                Page::displaySlice(OutputDev*, double, double, int,
bool, bool, int, int, int, int, bool, Catalog*, bool (*)(void*),
void*, bool (*)(Annot*, void*), void*)
                Gfx::display(Object*, bool)
                Gfx::go(bool)
                Gfx::execOp(Object*, Object*, int)
                Gfx::opShowSpaceText(Object*, int)
                Gfx::doShowText(GooString*)
                SplashOutputDev::drawChar(GfxState*, double, double,
double, double, double, double, unsigned int, int, unsigned int*, int)
               |
               |--99.76%-- Splash::fillChar(double, double, int, SplashFont*)
               |          SplashFTFont::getGlyph(int, int, int,
SplashGlyphBitmap*, int, int, SplashClip*, SplashClipResult*)
               |          SplashFont::getGlyph(int, int, int,
SplashGlyphBitmap*, int, int, SplashClip*, SplashClipResult*)
               |          SplashFTFont::makeGlyph(int, int, int,
SplashGlyphBitmap*, int, int, SplashClip*, SplashClipResult*)
               |          |
               |          |--59.74%-- FT_Render_Glyph
               |          |          |
               |          |          |--99.80%-- FT_Render_Glyph_Internal