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, 8 insertions, 0 deletions

diff --git a/src/gallium/drivers/virgl/virgl_resource.h b/src/gallium/drivers/virgl/virgl_resource.h
index 86eb2322513..c3374fbef70 100644
--- a/src/gallium/drivers/virgl/virgl_resource.h
+++ b/src/gallium/drivers/virgl/virgl_resource.h
@@ -73,10 +73,14 @@ struct virgl_resource {
 enum virgl_transfer_map_type {
    VIRGL_TRANSFER_MAP_ERROR = -1,
    VIRGL_TRANSFER_MAP_HW_RES,
+
    /* Map a range of a staging buffer. The updated contents should be transferred
     * with a copy transfer.
     */
    VIRGL_TRANSFER_MAP_STAGING,
+
+   /* Reallocate the underlying virgl_hw_res. */
+   VIRGL_TRANSFER_MAP_REALLOC,
 };
 
 struct virgl_transfer {
@@ -187,4 +191,8 @@ void virgl_resource_dirty(struct virgl_resource *res, uint32_t level);
 void *virgl_transfer_uploader_map(struct virgl_context *vctx,
                                   struct virgl_transfer *vtransfer);
 
+bool
+virgl_resource_realloc(struct virgl_context *vctx,
+                       struct virgl_resource *res);
+
 #endif