• Alyssa Rosenzweig's avatar
    panfrost: Replace pantrace with direct decoding · fc7bcee8
    Alyssa Rosenzweig authored
    History lesson! In the early days of a Panfrost, we had a library
    independent of the driver called `panwrap` which would be LD_PRELOAD'ed
    into a driver to decode its cmdstream in real-time. When upstreaming
    Panfrost, we realized that we would much rather have this decode
    functionality maintained in-tree to avoid divergence, but that we could
    not upstream panwrap because of its use with the legacy API. So we
    instead dumped GPU memory to the filesystem with an out-of-tree panwrap,
    and decoded that with the in-tree pandecode module. When we migrated to
    the new kernel, we just added support for doing this memory dump
    directly from the driver (via a module "pantrace").
    
    This works, but dumping memory every frame is sloooooooooooooow and
    error-prone. I figured if we have pandecode in-tree, we might as well
    link to it directly in the driver, allowing us to decode Panfrost's
    command streams without dumping memory to the filesystem first. This
    cleans up the code *substantially* and improves dumping performance by a
    HUGE margin. I'm talking "several seconds per frame" to "dumping in
    real-time" kind of jump.
    
    Note to users: this removes the environmental option "PANTRACE_BASE".
    Instead, for equivalent functionality set "PAN_MESA_DEBUG=trace" and
    redirect stdout to the file of your choosing.
    
    This should be debugging Panfrost much more pleasant.
    Signed-off-by: Alyssa Rosenzweig's avatarAlyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
    fc7bcee8
decode.c 78.8 KB