[Mesa-dev] [EGL android: accquire fence implementation 1/2] i965: Return the last fence if the batch buffer is empty and nothing to be flushed when _intel_batchbuffer_flush_fence.

[Emil Velikov]

Hi Zhongmin,

Is the issue resolved by the EGL patch alone? Worth sticking with that for now?

I think this patch will cause some noticeable overhead - see below for details.


On 21 July 2017 at 04:08, Zhongmin Wu <zhongmin.wu at intel.com> wrote:
> Always save the last fence in the brw context when flushing
> buffer. If the buffer is nothing to be flushed, then return
> the last fence when asked for.
>
> Change-Id: Ic47035bcd1a27e402609afd9e2d1e3972548b97d
> Signed-off-by: Zhongmin Wu <zhongmin.wu at intel.com>
> ---
>  src/mesa/drivers/dri/i965/brw_context.c       |    5 +++++
>  src/mesa/drivers/dri/i965/brw_context.h       |    1 +
>  src/mesa/drivers/dri/i965/intel_batchbuffer.c |   16 ++++++++++++++--
>  3 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
> index 5433f90..ed0b056 100644
> --- a/src/mesa/drivers/dri/i965/brw_context.c
> +++ b/src/mesa/drivers/dri/i965/brw_context.c
> @@ -1086,6 +1086,8 @@ brwCreateContext(gl_api api,
>     ctx->VertexProgram._MaintainTnlProgram = true;
>     ctx->FragmentProgram._MaintainTexEnvProgram = true;
>
> +   brw->out_fence_fd = -1;
> +
>     brw_draw_init( brw );
>
>     if ((flags & __DRI_CTX_FLAG_DEBUG) != 0) {
> @@ -1169,6 +1171,9 @@ intelDestroyContext(__DRIcontext * driContextPriv)
>     brw->throttle_batch[1] = NULL;
>     brw->throttle_batch[0] = NULL;
>
> +   if (brw->out_fence_fd >= 0)
> +      close(brw->out_fence_fd);
> +
>     driDestroyOptionCache(&brw->optionCache);
>
>     /* free the Mesa context */
> diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
> index dc4bc8f..692ea2c 100644
> --- a/src/mesa/drivers/dri/i965/brw_context.h
> +++ b/src/mesa/drivers/dri/i965/brw_context.h
> @@ -1217,6 +1217,7 @@ struct brw_context
>
>     __DRIcontext *driContext;
>     struct intel_screen *screen;
> +   int out_fence_fd;
>  };
>
>  /* brw_clear.c */
> diff --git a/src/mesa/drivers/dri/i965/intel_batchbuffer.c b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
> index 62d2fe8..d342e5d 100644
> --- a/src/mesa/drivers/dri/i965/intel_batchbuffer.c
> +++ b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
> @@ -648,9 +648,18 @@ do_flush_locked(struct brw_context *brw, int in_fence_fd, int *out_fence_fd)
>           /* Add the batch itself to the end of the validation list */
>           add_exec_bo(batch, batch->bo);
>
> +         if (brw->out_fence_fd >= 0) {
> +            close(brw->out_fence_fd);
> +            brw->out_fence_fd = -1;
> +         }
> +
> +         int fd = -1;
>           ret = execbuffer(dri_screen->fd, batch, hw_ctx,
>                            4 * USED_BATCH(*batch),
> -                          in_fence_fd, out_fence_fd, flags);
> +                          in_fence_fd, &fd, flags);
execbuffer() creates an out fence if the "out_fence_fd" pointer is non-NULL.
Hence with this patch we'will create a fence for each
_intel_batchbuffer_flush_fence() invocation...

Not sure how costly that will be though :-\

-Emil