drm/i915: Preallocate enough space for the average request

Rather than being interrupted when we run out of space halfway through
the request, and having to restart from the beginning (and returning to
userspace), flush a little more free space when we prepare the request.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-15-git-send-email-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 4139858323513a742b930bb3f8baff829c9bc377..4dedeaa3c788ed5893fca1bbb104022a2c8ea6b6 100644 (file)
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -700,6 +700,12 @@ int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request
 {
        int ret;
 
+       /* Flush enough space to reduce the likelihood of waiting after
+        * we start building the request - in which case we will just
+        * have to repeat work.
+        */
+       request->reserved_space += MIN_SPACE_FOR_ADD_REQUEST;
+
        request->ringbuf = request->ctx->engine[request->engine->id].ringbuf;
 
        if (i915.enable_guc_submission) {
@@ -725,6 +731,7 @@ int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request
        if (ret)
                goto err_unpin;
 
+       request->reserved_space -= MIN_SPACE_FOR_ADD_REQUEST;
        return 0;
 
 err_unpin:

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index c2a699230809caa89bcdd865c29d12f42f6997f5..b5e79ac29ebc9e824a6855e009f88dac3e557522 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2339,8 +2339,22 @@ int intel_engine_idle(struct intel_engine_cs *engine)
 
 int intel_ring_alloc_request_extras(struct drm_i915_gem_request *request)
 {
+       int ret;
+
+       /* Flush enough space to reduce the likelihood of waiting after
+        * we start building the request - in which case we will just
+        * have to repeat work.
+        */
+       request->reserved_space += MIN_SPACE_FOR_ADD_REQUEST;
+
        request->ringbuf = request->engine->buffer;
-       return intel_ring_begin(request, 0);
+
+       ret = intel_ring_begin(request, 0);
+       if (ret)
+               return ret;
+
+       request->reserved_space -= MIN_SPACE_FOR_ADD_REQUEST;
+       return 0;
 }
 
 static int wait_for_space(struct drm_i915_gem_request *req, int bytes)