Re: [gst-devel] mini filesrc patch

[<vishnu@po...>]

On Mon, Oct 01, 2001 at 12:55:05PM -0700, Erik Walthinsen wrote:
> On Sun, 30 Sep 2001 vishnu@... wrote:
> > i don't understand why touch is currently set to TRUE.
> > -  src->touch = TRUE;
> > +  src->touch = FALSE;
> 
> The touch param causes filesrc to read a word at the beginning of each
> page.  This forces the kernel to read the data from the disk into
> bufcache.

Yah ..,

> The reason this is necessary and on by default is that without
> it, the first element to touch the data has to wait for the data to come
> off disk.  In a bandwidth/latency critical situation, you'll have a thread
> containing the filesrc and one or more threads containing the rest of the
> pipeline.  The goal of this is to use the filesrc thread to manage the
> disk I/O, which when using mmap means touching the data, which isolates
> the latencies of doing so in their own thread, behind a queue that can
> help absorb them.

OK, but i'm not convinced that this is *always* the right thing to do.

Will you accept a patch to make 'touch' a gobject property?

-- 
Victory to the Divine Mother!!
  http://sahajayoga.org

Re: [gst-devel] mini filesrc patch

[Erik Walthinsen <omega@te...>]

On Sun, 30 Sep 2001 vishnu@... wrote:

> i don't understand why touch is currently set to TRUE.
> -  src->touch = TRUE;
> +  src->touch = FALSE;

The touch param causes filesrc to read a word at the beginning of each
page.  This forces the kernel to read the data from the disk into
bufcache.  The reason this is necessary and on by default is that without
it, the first element to touch the data has to wait for the data to come
off disk.  In a bandwidth/latency critical situation, you'll have a thread
containing the filesrc and one or more threads containing the rest of the
pipeline.  The goal of this is to use the filesrc thread to manage the
disk I/O, which when using mmap means touching the data, which isolates
the latencies of doing so in their own thread, behind a queue that can
help absorb them.

      Erik Walthinsen <omega@...> - System Administrator
        __
       /  \                GStreamer - The only way to stream!
      |    | M E G A        ***** http://gstreamer.net/ *****
      _\  /_

Re: [gst-devel] Re: libgst.so needs -lm in head

[Steve Baker <stevebaker_org@ya...>]

On Sun, 2001-09-30 at 01:01, Erik Walthinsen wrote:
> On 29 Sep 2001, Steve Baker wrote:
> 
> > gstdparammanager has to be in core as it is coupled with gstelement and
> > it has macros that any plugin might use.
> 
> Is there any way it might be made an external subsystem?  I haven't looked
> at how it's integrated, but it would be good if it can be limitted to just
> the plugins that use it.  Dunno how feasible that is, but something to
> look at maybe.

Currently the only real integration is:
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/gstreamer/gstreamer/gst/gstelement.h.diff?r1=1.57&r2=1.58

The only thing I can think of adding to gstelement is maybe a getter and
a call to unref the dparam_manager during the element's dispose.

I can see how dparams could be taken out of core entirely if elements
were responsible for storing and disposing their own instance of
dparam_manager. They would also have to link to libgstcontrol. I don't
see this as much of a burden on plugin writers. 

The only downside I see is for elements which might be useful in an
embedded environment AND which benefit from dparams in a desktop
environment.  

Erik may be able to confirm this but I suspect that elements destined
for embedded environments would be written from scratch or maybe
forked&slimmed to save size.  If this is the case then we wouldn't need
to think twice about adding dparams support to any given plugin.

Oh, and if we do this I really will have to move sinesrc out of core ;-)

cheers


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[gst-devel] mini filesrc patch

[<vishnu@po...>]

i don't understand why touch is currently set to TRUE.

--- joshua/gst/elements/gstfilesrc.c	Sun Sep 30 17:03:26 2001
+++ current/gst/elements/gstfilesrc.c	Sun Sep 30 17:18:38 2001
@@ -254,7 +254,7 @@ gst_filesrc_init (GstFileSrc *src)
 
   src->curoffset = 0;
   src->block_size = 4096;
-  src->touch = TRUE;
+  src->touch = FALSE;
 
   src->mapbuf = NULL;
   src->mapsize = 4 * 1024 * 1024;		// default is 4MB

-- 
Victory to the Divine Mother!!
  http://sahajayoga.org