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

[Ole André Vadla Ravnås]

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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