[Mesa-dev] [PATCH] [RFC v2] mesa/glthread: Call unmarshal_batch directly in glthread_finish when batch queue is empty.

[Bartosz Tomczyk]

This avoids costly thread synchronisation. With this fix games that previously regressed with mesa_glthread=true like xonotic or grid autosport.
Could someone test if games that benefit from glthread didn't regress?
---
 src/mesa/main/glthread.c | 49 +++++++++++++++++++++++++++++++++---------------
 1 file changed, 34 insertions(+), 15 deletions(-)

diff --git a/src/mesa/main/glthread.c b/src/mesa/main/glthread.c
index 06115b916d..eef7202f01 100644
--- a/src/mesa/main/glthread.c
+++ b/src/mesa/main/glthread.c
@@ -194,18 +194,11 @@ _mesa_glthread_restore_dispatch(struct gl_context *ctx)
    }
 }
 
-void
-_mesa_glthread_flush_batch(struct gl_context *ctx)
+static void
+_mesa_glthread_flush_batch_no_lock(struct gl_context *ctx)
 {
    struct glthread_state *glthread = ctx->GLThread;
-   struct glthread_batch *batch;
-
-   if (!glthread)
-      return;
-
-   batch = glthread->batch;
-   if (!batch->used)
-      return;
+   struct glthread_batch *batch = glthread->batch;
 
    /* Immediately reallocate a new batch, since the next marshalled call would
     * just do it.
@@ -223,10 +216,26 @@ _mesa_glthread_flush_batch(struct gl_context *ctx)
       return;
    }
 
-   pthread_mutex_lock(&glthread->mutex);
    *glthread->batch_queue_tail = batch;
    glthread->batch_queue_tail = &batch->next;
    pthread_cond_broadcast(&glthread->new_work);
+
+}
+void
+_mesa_glthread_flush_batch(struct gl_context *ctx)
+{
+   struct glthread_state *glthread = ctx->GLThread;
+   struct glthread_batch *batch;
+
+   if (!glthread)
+      return;
+
+   batch = glthread->batch;
+   if (!batch->used)
+      return;
+
+   pthread_mutex_lock(&glthread->mutex);
+   _mesa_glthread_flush_batch_no_lock(ctx);
    pthread_mutex_unlock(&glthread->mutex);
 }
 
@@ -252,12 +261,22 @@ _mesa_glthread_finish(struct gl_context *ctx)
    if (pthread_self() == glthread->thread)
       return;
 
-   _mesa_glthread_flush_batch(ctx);
-
    pthread_mutex_lock(&glthread->mutex);
 
-   while (glthread->batch_queue || glthread->busy)
-      pthread_cond_wait(&glthread->work_done, &glthread->mutex);
+   if (!(glthread->batch_queue || glthread->busy))
+   {
+      if (glthread->batch && glthread->batch->used)
+      {
+         glthread_unmarshal_batch(ctx, glthread->batch);
+      }
+      glthread_allocate_batch(ctx);
+   }
+   else
+   {
+      _mesa_glthread_flush_batch_no_lock(ctx);
+      while (glthread->batch_queue || glthread->busy)
+         pthread_cond_wait(&glthread->work_done, &glthread->mutex);
+   }
 
    pthread_mutex_unlock(&glthread->mutex);
 }
-- 
2.12.2