Re: [ft] Minimizing small file reads

[suzuki toshiya]

Hi,

As Mickey Gabel has proposed, it is possible to load a font face from
a memory image that is copied from a font file.

Please check FT_Open_Face() API
http://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html#FT_Open_Face
and its argument
http://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html#FT_Open_Args
It is possible to make a FT_Face object from a memory image.

If you want a concrete example, please check an implementation of
a private internal function open_face_from_buffer() in src/base/ftobjs.c.

Regards,
mpsuzuki


☂Josh Chia (谢任中) wrote:
> Hi
>
> If you're talking about mmap(), yes my system has mmap, but I'll have to
> check whether I have it enabled in my freetype build.  I notice that
> freetype is reading little pieces of data, like a long here and there.  I
> also see larger chunks of 4k being read, but ideally, I would like to have
> everything in memory so that I don't need any calls to read() after some
> initial read(s).  Perhaps, there's a way to prefetch entire font files?
>
> If mmap() can be used to avoid small reads, I should probably investigate
> how to make use of it.
>
> Josh
>
> On Mon, Nov 17, 2008 at 9:34 PM, suzuki toshiya
> <address@hidden>wrote:
>
>   
> > Hi,
> >
> > In the system supporting memmap() and FreeType2 is configured
> > to use it, the number of system call would be much reduced in
> > comparison with the system without memmap. In the target platform
> > which you're working for, memmap() is available? Or, available
> > and configured to use it, but you think still too many read
> > system call is executed?
> >
> > Regards,
> > mpsuzuki
> >
> > ☂Josh Chia (谢任中) wrote (2008/11/18 10:39):
> >
> >     
> > > Hi,
> > >
> > > I notice that freetype makes a lot of small reads, resulting in a lot of
> > > SYS_read calls.  I'm using freetype in an app that runs in a ptrace
> > > sandbox,
> > > so performance is sensitive to system calls.  Is there a simple way to
> > > prevent the numerous small reads (via ft_ansi_stream_io), such as
> > > configuring freetype to prefetch into a large buffer when reading, and
> > > making it assume that font files never change?  Will I need to make some
> > > configuration changes or do I need to make code changes?  Thanks!
> > >
> > > Josh
> > >
> > >
> > >
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