[Mesa-dev] [PATCH 02/12] i965: Check last known busy status on bo before asking the kernel

[Chris Wilson]

If we know the bo is idle (that is we have no submitted a command buffer
referencing this bo since the last query) we can skip asking the kernel.
Note this may report a false negative if the target is being shared
between processes (exported via dmabuf or flink). To allow the caller
control over using the last known flag, the query is split into two.

v2: Check against external bo before trusting our own tracking.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Kenneth Graunke <kenneth at whitecape.org>
Cc: Matt Turner <mattst88 at gmail.com>
---
 src/mesa/drivers/dri/i965/brw_bufmgr.c | 42 ++++++++++++++++++++++++----------
 src/mesa/drivers/dri/i965/brw_bufmgr.h | 11 +++++++--
 2 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.c b/src/mesa/drivers/dri/i965/brw_bufmgr.c
index 844ccaf1e5..5c7647f8bc 100644
--- a/src/mesa/drivers/dri/i965/brw_bufmgr.c
+++ b/src/mesa/drivers/dri/i965/brw_bufmgr.c
@@ -196,22 +196,40 @@ bucket_for_size(struct brw_bufmgr *bufmgr, uint64_t size)
    return NULL;
 }
 
-int
+static int
+__brw_bo_busy(struct brw_bo *bo)
+{
+   struct drm_i915_gem_busy busy = { bo->gem_handle };
+
+   if (bo->idle && !bo->external)
+      return 0;
+
+   /* If we hit an error here, it means that bo->gem_handle is invalid.
+    * Treat it as being idle (busy.busy is left as 0) and move along.
+    */
+   drmIoctl(bo->bufmgr->fd, DRM_IOCTL_I915_GEM_BUSY, &busy);
+
+   bo->idle = !busy.busy;
+   return busy.busy;
+}
+
+bool
 brw_bo_busy(struct brw_bo *bo)
 {
-   struct brw_bufmgr *bufmgr = bo->bufmgr;
-   struct drm_i915_gem_busy busy;
-   int ret;
+   return __brw_bo_busy(bo);
+}
 
-   memclear(busy);
-   busy.handle = bo->gem_handle;
+bool
+brw_bo_map_busy(struct brw_bo *bo, unsigned flags)
+{
+   unsigned mask;
 
-   ret = drmIoctl(bufmgr->fd, DRM_IOCTL_I915_GEM_BUSY, &busy);
-   if (ret == 0) {
-      bo->idle = !busy.busy;
-      return busy.busy;
-   }
-   return false;
+   if (flags & MAP_WRITE)
+      mask = ~0u;
+   else
+      mask = 0xffff;
+
+   return __brw_bo_busy(bo) & mask;
 }
 
 int
diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.h b/src/mesa/drivers/dri/i965/brw_bufmgr.h
index d09bc74c9c..9848fe9268 100644
--- a/src/mesa/drivers/dri/i965/brw_bufmgr.h
+++ b/src/mesa/drivers/dri/i965/brw_bufmgr.h
@@ -271,10 +271,17 @@ int brw_bo_get_tiling(struct brw_bo *bo, uint32_t *tiling_mode,
 int brw_bo_flink(struct brw_bo *bo, uint32_t *name);
 
 /**
- * Returns 1 if mapping the buffer for write could cause the process
+ * Returns false if mapping the buffer is not in active use by the gpu.
+ * If it returns true, any mapping for for write could cause the process
  * to block, due to the object being active in the GPU.
  */
-int brw_bo_busy(struct brw_bo *bo);
+bool brw_bo_busy(struct brw_bo *bo);
+
+/**
+ * Returns true if mapping the buffer for the set of flags (i.e. MAP_READ or
+ * MAP_WRITE) will cause the process to block.
+ */
+bool brw_bo_map_busy(struct brw_bo *bo, unsigned flags);
 
 /**
  * Specify the volatility of the buffer.
-- 
2.13.3