virgl: better support for PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE

When the resource to be mapped is busy and the backing storage can
be discarded, reallocate the backing storage to avoid waiting.

In this new path, we allocate a new buffer, emit a state change,
write, and add the transfer to the queue .  In the
PIPE_TRANSFER_DISCARD_RANGE path, we suballocate a staging buffer,
write, and emit a copy_transfer (which may allocate, memcpy, and
blit internally).  The win might not always be clear.  But another
win comes from that the new path clears res->valid_buffer_range and
does not clear res->clean_mask.  This makes it much more preferable
in scenarios such as

  access = enough_space ? GL_MAP_UNSYNCHRONIZED_BIT :
                          GL_MAP_INVALIDATE_BUFFER_BIT;
  glMapBufferRange(..., GL_MAP_WRITE_BIT | access);
  memcpy(...); // append new data
  glUnmapBuffer(...);

Signed-off-by: Chia-I Wu <[email protected]>
Reviewed-by: Alexandros Frantzis <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/gallium/drivers/virgl/virgl_buffer.c b/src/gallium/drivers/virgl/virgl_buffer.c
index ddb632db483..ed001722ab4 100644
--- a/src/gallium/drivers/virgl/virgl_buffer.c
+++ b/src/gallium/drivers/virgl/virgl_buffer.c
@@ -47,6 +47,13 @@ static void *virgl_buffer_transfer_map(struct pipe_context *ctx,
 
    map_type = virgl_resource_transfer_prepare(vctx, trans);
    switch (map_type) {
+   case VIRGL_TRANSFER_MAP_REALLOC:
+      if (!virgl_resource_realloc(vctx, vbuf)) {
+         map_addr = NULL;
+         break;
+      }
+      vs->vws->resource_reference(vs->vws, &trans->hw_res, vbuf->hw_res);
+      /* fall through */
    case VIRGL_TRANSFER_MAP_HW_RES:
       trans->hw_res_map = vs->vws->resource_map(vs->vws, vbuf->hw_res);
       if (trans->hw_res_map)