[Mesa-dev] [PATCH v2 00/37] panfrost: Support batch pipelining

[Connor Abbott]

As a drive-by comment, in case you didn't know, the "standard"
solution for avoiding flushing when BO's are written by the CPU (e.g.
uniform buffer updates) as documented in ARM's performance guide is to
add a copy-on-write mechanism, so that you have "shadow" BO's when the
original BO is modified by the user. I believe this is implemented in
freedreno, at least there was a talk about it at XDC a few years ago.

On Mon, Sep 16, 2019 at 4:37 PM Boris Brezillon
<boris.brezillon at collabora.com> wrote:
>
> Hello,
>
> This is the second attempt at supporting batch pipelining. This time I
> implemented it using a dependency graph (as suggested by Alyssa and
> Steven) so that batch submission can be delayed even more: the only
> time we flush batches now is when we have an explicit flush or when
> the CPU needs to access a BO (we might want to tweak that a bit to
> avoid the extra latency incurred by this solution). With that in place
> we hope to increase GPU utilization.
>
> A few words about the patches in this series:
>
> * Like the previous version, this series is a mix of cleanups and
>   functional changes. Most of them should be pretty trivial to review
>   and I intend to merge them independently once they have receive
>   proper review (to avoid having to send another patch bomb like this
>   one).
>
> * The "rework BO API" batch has been split to ease review
>
> * Patches 35 and 36 are not mandatory, but I remember reading (I think
>   it was Steven who mentioned that) that draw order matters when
>   queueing render operations for different frames (frame N should
>   ideally be ready before frame N+1). Not sure if enforcing draw call
>   order is enough to guarantee that rendering of frame N always
>   finishes before frame N+1 though.
>
> Regards,
>
> Boris
>
> Boris Brezillon (37):
>   panfrost: Stop exposing internal panfrost_*_batch() functions
>   panfrost: Use the correct type for the bo_handle array
>   panfrost: Add missing panfrost_batch_add_bo() calls
>   panfrost: Add polygon_list to the batch BO set at allocation time
>   panfrost: Kill a useless memset(0) in panfrost_create_context()
>   panfrost: Stop passing has_draws to panfrost_drm_submit_vs_fs_batch()
>   panfrost: Get rid of pan_drm.c
>   panfrost: Move panfrost_bo_{reference,unreference}() to pan_bo.c
>   panfrost: s/PAN_ALLOCATE_/PAN_BO_/
>   panfrost: Move the BO API to its own header
>   panfrost: Stop exposing panfrost_bo_cache_{fetch,put}()
>   panfrost: Don't check if BO is mmaped before calling
>     panfrost_bo_mmap()
>   panfrost: Stop passing screen around for BO operations
>   panfrost: Stop using panfrost_bo_release() outside of pan_bo.c
>   panfrost: Add panfrost_bo_{alloc,free}()
>   panfrost: Don't return imported/exported BOs to the cache
>   panfrost: Make sure the BO is 'ready' when picked from the cache
>   panfrost: Add flags to reflect the BO imported/exported state
>   panfrost: Add the panfrost_batch_create_bo() helper
>   panfrost: Add FBO BOs to batch->bos earlier
>   panfrost: Allocate tiler and scratchpad BOs per-batch
>   panfrost: Extend the panfrost_batch_add_bo() API to pass access flags
>   panfrost: Make panfrost_batch->bos a hash table
>   panfrost: Cache GPU accesses to BOs
>   panfrost: Add a batch fence
>   panfrost: Use the per-batch fences to wait on the last submitted batch
>   panfrost: Add a panfrost_freeze_batch() helper
>   panfrost: Start tracking inter-batch dependencies
>   panfrost: Prepare panfrost_fence for batch pipelining
>   panfrost: Add a panfrost_flush_all_batches() helper
>   panfrost: Add a panfrost_flush_batches_accessing_bo() helper
>   panfrost: Kill the explicit serialization in panfrost_batch_submit()
>   panfrost: Get rid of the flush in panfrost_set_framebuffer_state()
>   panfrost: Do fine-grained flushing when preparing BO for CPU accesses
>   panfrost: Rename ctx->batches into ctx->fbo_to_batch
>   panfrost: Take draw call order into account
>   panfrost/ci: New tests are passing
>
>  .../drivers/panfrost/ci/expected-failures.txt |   4 -
>  src/gallium/drivers/panfrost/meson.build      |   1 -
>  src/gallium/drivers/panfrost/pan_allocate.c   |  22 +-
>  src/gallium/drivers/panfrost/pan_allocate.h   |  20 -
>  src/gallium/drivers/panfrost/pan_assemble.c   |   3 +-
>  src/gallium/drivers/panfrost/pan_blend_cso.c  |  13 +-
>  src/gallium/drivers/panfrost/pan_bo.c         | 331 +++++++-
>  src/gallium/drivers/panfrost/pan_bo.h         | 130 +++
>  src/gallium/drivers/panfrost/pan_compute.c    |   2 +-
>  src/gallium/drivers/panfrost/pan_context.c    | 175 ++--
>  src/gallium/drivers/panfrost/pan_context.h    |  22 +-
>  src/gallium/drivers/panfrost/pan_drm.c        | 394 ---------
>  src/gallium/drivers/panfrost/pan_fragment.c   |   3 -
>  src/gallium/drivers/panfrost/pan_instancing.c |   6 +-
>  src/gallium/drivers/panfrost/pan_job.c        | 760 ++++++++++++++++--
>  src/gallium/drivers/panfrost/pan_job.h        |  85 +-
>  src/gallium/drivers/panfrost/pan_mfbd.c       |   1 +
>  src/gallium/drivers/panfrost/pan_resource.c   |  65 +-
>  src/gallium/drivers/panfrost/pan_resource.h   |   6 -
>  src/gallium/drivers/panfrost/pan_screen.c     |  91 ++-
>  src/gallium/drivers/panfrost/pan_screen.h     |  62 +-
>  src/gallium/drivers/panfrost/pan_sfbd.c       |   1 +
>  src/gallium/drivers/panfrost/pan_varyings.c   |   6 +-
>  23 files changed, 1456 insertions(+), 747 deletions(-)
>  create mode 100644 src/gallium/drivers/panfrost/pan_bo.h
>  delete mode 100644 src/gallium/drivers/panfrost/pan_drm.c
>
> --
> 2.21.0
>
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