[gstreamer-bugs] [Bug 345720] New: Bad performance playing files off CD

[GStreamer (bugzilla.gnome.org)]

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 GStreamer | gstreamer (core) | Ver: HEAD CVS

           Summary: Bad performance playing files off CD
           Product: GStreamer
           Version: HEAD CVS
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gstreamer (core)
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: thaytan at mad.scientist.com
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


I'm seeing really bad playback of an AVI file directly off CD. I think it is
caused by the access pattern that results. Buffers are delivered to avidemux,
which does subbuffering and puts things in queues.

A while later, the audio and video decoder start accessing those pages. This
means that now avidemux and the audio/video decoders are trying to access pages
in quite different locations. Unfortunately, filesrc specified (using madvise)
that we'd be doing sequential access, so the kernel is being forced to page-in
things it already threw away.

Turning off MADV_SEQUENTIAL and touching each page to read it in immediately
improves things greatly. Attaching a patch.


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