gallium: avoid mapping same vertex buffer in subsequent frames

Quite a few util modules were maintaining a single vertex buffer over multiple
frames, and potentially reusing it in subsequent frames.  Unfortunately that
would force us into syncrhonous rendering as the buffer manager would be
forced to wait for the previous rendering to complete prior to allowing the
map.

This resolves that issue, but requires the state tracker to issue a few new
flush() calls at the end of each frame.

1 files changed, 28 insertions, 3 deletions

diff --git a/src/mesa/state_tracker/st_cb_clear.c b/src/mesa/state_tracker/st_cb_clear.c
index bc3055c3fdf..b6cea161634 100644
--- a/src/mesa/state_tracker/st_cb_clear.c
+++ b/src/mesa/state_tracker/st_cb_clear.c
@@ -148,12 +148,18 @@ draw_quad(GLcontext *ctx,
 {
    struct st_context *st = ctx->st;
    struct pipe_context *pipe = st->pipe;
+   const GLuint max_slots = 1024 / sizeof(st->clear.vertices);
    GLuint i;
    void *buf;
 
+   if (st->clear.vbuf_slot >= max_slots) {
+      pipe_buffer_reference(pipe->screen, &st->clear.vbuf, NULL);
+      st->clear.vbuf_slot = 0;
+   }
+
    if (!st->clear.vbuf) {
       st->clear.vbuf = pipe_buffer_create(pipe->screen, 32, PIPE_BUFFER_USAGE_VERTEX,
-                                          sizeof(st->clear.vertices));
+                                          max_slots * sizeof(st->clear.vertices));
    }
 
    /* positions */
@@ -181,14 +187,23 @@ draw_quad(GLcontext *ctx,
 
    /* put vertex data into vbuf */
    buf = pipe_buffer_map(pipe->screen, st->clear.vbuf, PIPE_BUFFER_USAGE_CPU_WRITE);
-   memcpy(buf, st->clear.vertices, sizeof(st->clear.vertices));
+
+   memcpy((char *)buf + st->clear.vbuf_slot * sizeof(st->clear.vertices), 
+          st->clear.vertices, 
+          sizeof(st->clear.vertices));
+
    pipe_buffer_unmap(pipe->screen, st->clear.vbuf);
 
    /* draw */
-   util_draw_vertex_buffer(pipe, st->clear.vbuf,
+   util_draw_vertex_buffer(pipe, 
+                           st->clear.vbuf, 
+                           st->clear.vbuf_slot * sizeof(st->clear.vertices),
                            PIPE_PRIM_TRIANGLE_FAN,
                            4,  /* verts */
                            2); /* attribs/vert */
+
+   /* Increment slot */
+   st->clear.vbuf_slot++;
 }
 
 
@@ -508,6 +523,16 @@ clear_depth_stencil_buffer(GLcontext *ctx, struct gl_renderbuffer *rb)
 }
 
 
+void st_flush_clear( struct st_context *st )
+{
+   /* Release vertex buffer to avoid synchronous rendering if we were
+    * to map it in the next frame.
+    */
+   pipe_buffer_reference(st->pipe->screen, &st->clear.vbuf, NULL);
+   st->clear.vbuf_slot = 0;
+}
+ 
+
 
 /**
  * Called via ctx->Driver.Clear()