[Mesa-dev] [PATCH 4/4] i965: Add support for GL_ARB_buffer_storage.

[Eric Anholt]

It turns out we can allow COHERENT storage/mappings all the time,
regardless of LLC vs non-LLC.  It just means never using temporary
mappings to avoid GPU stalls, and on non-LLC we have to use the GTT intead
of CPU mappings.  If we were to use CPU maps on non-LLC (which might be
useful if apps end up using buffer_storage on PBO reads, to avoid WC read
slowness), those would be PERSISTENT but not COHERENT, but doing that
would require us driving the clflushes from userspace somehow.

Using this in glamor, I got a 29.5361% +/- 2.74092% improvement in x11perf
-aa10text (n=489).
---
 docs/GL3.txt                                     | 2 +-
 src/mesa/drivers/dri/i965/intel_buffer_objects.c | 9 +++++++--
 src/mesa/drivers/dri/i965/intel_extensions.c     | 1 +
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/docs/GL3.txt b/docs/GL3.txt
index 5261eda..45db98f 100644
--- a/docs/GL3.txt
+++ b/docs/GL3.txt
@@ -170,7 +170,7 @@ GL 4.4:
 
   GLSL 4.4                                             not started
   GL_MAX_VERTEX_ATTRIB_STRIDE                          not started
-  GL_ARB_buffer_storage                                DONE (r300, r600, radeonsi)
+  GL_ARB_buffer_storage                                DONE (i965, r300, r600, radeonsi)
   GL_ARB_clear_texture                                 not started
   GL_ARB_enhanced_layouts                              not started
   GL_ARB_multi_bind                                    started (Fredrik Höglund)
diff --git a/src/mesa/drivers/dri/i965/intel_buffer_objects.c b/src/mesa/drivers/dri/i965/intel_buffer_objects.c
index 260308a..96dacde 100644
--- a/src/mesa/drivers/dri/i965/intel_buffer_objects.c
+++ b/src/mesa/drivers/dri/i965/intel_buffer_objects.c
@@ -401,8 +401,12 @@ intel_bufferobj_map_range(struct gl_context * ctx,
     * doesn't require the current contents of that range, make a new
     * BO, and we'll copy what they put in there out at unmap or
     * FlushRange time.
+    *
+    * That is, unless they're looking for a persistent mapping -- we would
+    * need to do blits in the MemoryBarrier call, and it's easier to just do a
+    * GPU stall and do a mapping.
     */
-   if (!(access & GL_MAP_UNSYNCHRONIZED_BIT) &&
+   if (!(access & (GL_MAP_UNSYNCHRONIZED_BIT | GL_MAP_PERSISTENT_BIT)) &&
        (access & GL_MAP_INVALIDATE_RANGE_BIT) &&
        drm_intel_bo_busy(intel_obj->buffer)) {
       /* Ensure that the base alignment of the allocation meets the alignment
@@ -429,7 +433,8 @@ intel_bufferobj_map_range(struct gl_context * ctx,
 
    if (access & GL_MAP_UNSYNCHRONIZED_BIT)
       drm_intel_gem_bo_map_unsynchronized(intel_obj->buffer);
-   else if (!brw->has_llc && !(access & GL_MAP_READ_BIT)) {
+   else if (!brw->has_llc && (!(access & GL_MAP_READ_BIT) ||
+                              (access & GL_MAP_PERSISTENT_BIT))) {
       drm_intel_gem_bo_map_gtt(intel_obj->buffer);
       intel_bufferobj_mark_inactive(intel_obj);
    } else {
diff --git a/src/mesa/drivers/dri/i965/intel_extensions.c b/src/mesa/drivers/dri/i965/intel_extensions.c
index ef9aa55..860896a 100644
--- a/src/mesa/drivers/dri/i965/intel_extensions.c
+++ b/src/mesa/drivers/dri/i965/intel_extensions.c
@@ -162,6 +162,7 @@ intelInitExtensions(struct gl_context *ctx)
 
    assert(brw->gen >= 4);
 
+   ctx->Extensions.ARB_buffer_storage = true;
    ctx->Extensions.ARB_depth_buffer_float = true;
    ctx->Extensions.ARB_depth_clamp = true;
    ctx->Extensions.ARB_depth_texture = true;
-- 
1.9.rc1