[gst-devel] RE : Re: RE : Re: aligned(16) GstBuffer Payload ?

[SP GLE]

Hi,
I thought glib (with g_malloc()) was using malloc() to get memory but
this one was kept in a pool even if you issue a g_free(), in order to
reuse it if needed and improve performances.

Regards.

--- Ole André Vadla Ravnås <ole.andre.ravnas at tandberg.com> a écrit :

> Hi,
> 
> Just one small comment:
> 
> On Sun, 2007-10-14 at 17:32 +0200, SP GLE wrote:
> (...)
> > But switching GstBuffer to posix_memalign is not a good thing
> (IMHO), :
> > - GstBuffers are often allocated for a limited time, there are
> groups
> > of GstBuffers with the same size (eg before decoding, before
> encoding,
> > after...etc), so relying on g_slice dramatticaly improves
> performances
> > over malloc and posix_memalign. 
> 
> gst_buffer_new_and_alloc uses g_malloc, which calls the standard
> malloc
> unless g_mem_set_vtable has been called. And as far as I can tell
> GStreamer doesn't call this, so it should be fine. (Unless there are
> other issues.)
> 
> Cheers,
> Ole André
> 
> 
> > --- Stefan Kost <ensonic at hora-obscura.de> a écrit :
> > 
> > > hi,
> > > 
> > > David Schleef wrote:
> > > > On Fri, Oct 12, 2007 at 05:05:58PM +0200, SP GLE wrote:
> > > >> is there a way to get a GstBuffer with a configurable
> memaligned
> > > >> payload (aligned(16)), in order to use payload with SSE2 and
> other
> > > >> liboil methods (even if liboil can work on not aligned data,
> using
> > > >> aligned could speed up some processing).
> > > > 
> > > > There are very few situations where allocating aligned buffers
> to
> > > > use with liboil will result in faster performance.  Liboil was
> > > designed
> > > > to allow you to use it without thinking of such things.
> > > > 
> > > > In any case, you can create aligned buffers by allocating a
> normal
> > > > buffer with extra padding, and creating an appropriate
> subbuffer.
> > > > Alternately, you could create a subclass of GstBuffer similar
> to
> > > > the efence element in -good.  Or you could patch gstbuffer.c
> and
> > > > add a function similar to gst_buffer_new_and_alloc() that
> allocates
> > > > memory using posix_memalign() instead of mallc().
> > > > 
> > > I was recently looking at it. Unfortunately
> gst_buffer_new_and_malloc
> > > uses
> > > g_malloc and g_free (we need to fix the docs regarding this).
> data
> > > allocated
> > > using posix_memalign() should be free'ed with free(). It could
> > > confuse glib if
> > > its free'ed with g_free(). So a subclass shoudl override the
> > > GstMiniObjectFinalizeFunction and properly release the memory. On
> the
> > > other hand
> > > I wonder if we should perhaps switch GstBuffer to use
> > > posix_memalign() and free().
> > > 
> > > Stefan
> > > 
> > > > 
> > > > 
> > > > dave...
> > > >
> > > 
> > 
> > 
> > 
> >      
>
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