drm/i915; Preallocate the lazy request

It is possible for us to be forced to perform an allocation for the lazy request whilst running the shrinker. This allocation may fail, leaving us unable to reclaim any memory leading to premature OOM. A neat solution to the problem is to preallocate the request at the same time as acquiring the seqno for the ring transaction. This means that we can report ENOMEM prior to touching the rings. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drm/i915; Preallocate the lazy request
It is possible for us to be forced to perform an allocation for the lazy request whilst running the shrinker. This allocation may fail, leaving us unable to reclaim any memory leading to premature OOM. A neat solution to the problem is to preallocate the request at the same time as acquiring the seqno for the ring transaction. This means that we can report ENOMEM prior to touching the rings. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Chris Wilson · Daniel Vetter
1 parent 1823521d2b
Showing 3 changed files with 15 additions and 5 deletions Side-by-side Diff
drivers/gpu/drm/i915/i915_gem.c
drivers/gpu/drm/i915/intel_ringbuffer.c
drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -2041,8 +2041,8 @@
 	if (ret)
 		return ret;
  
-	request = kmalloc(sizeof(*request), GFP_KERNEL);
-	if (request == NULL)
+	request = ring->preallocated_lazy_request;
+	if (WARN_ON(request == NULL))
 		return -ENOMEM;
  
 	/* Record the position of the start of the request so that
  
@@ -2053,10 +2053,8 @@
 	request_ring_position = intel_ring_get_tail(ring);
  
 	ret = ring->add_request(ring);
-	if (ret) {
-		kfree(request);
+	if (ret)
 		return ret;
-	}
  
 	request->seqno = intel_ring_get_seqno(ring);
 	request->ring = ring;
@@ -2095,6 +2093,7 @@
  
 	trace_i915_gem_request_add(ring, request->seqno);
 	ring->outstanding_lazy_seqno = 0;
+	ring->preallocated_lazy_request = NULL;
  
 	if (!dev_priv->ums.mm_suspended) {
 		i915_queue_hangcheck(ring->dev);
@@ -1498,6 +1498,16 @@
 	if (ring->outstanding_lazy_seqno)
 		return 0;
  
+	if (ring->preallocated_lazy_request == NULL) {
+		struct drm_i915_gem_request *request;
+
+		request = kmalloc(sizeof(*request), GFP_KERNEL);
+		if (request == NULL)
+			return -ENOMEM;
+
+		ring->preallocated_lazy_request = request;
+	}
+
 	return i915_gem_get_seqno(ring->dev, &ring->outstanding_lazy_seqno);
 }
  
@@ -140,6 +140,7 @@
 	/**
 	 * Do we have some not yet emitted requests outstanding?
 	 */
+	struct drm_i915_gem_request *preallocated_lazy_request;
 	u32 outstanding_lazy_seqno;
 	bool gpu_caches_dirty;
 	bool fbc_dirty;
...	...	@@ -2041,8 +2041,8 @@
2041	2041	if (ret)
2042	2042	return ret;
2043	2043
2044		- request = kmalloc(sizeof(*request), GFP_KERNEL);
2045		- if (request == NULL)
	2044	+ request = ring->preallocated_lazy_request;
	2045	+ if (WARN_ON(request == NULL))
2046	2046	return -ENOMEM;
2047	2047
2048	2048	/* Record the position of the start of the request so that
2049	2049
...	...	@@ -2053,10 +2053,8 @@
2053	2053	request_ring_position = intel_ring_get_tail(ring);
2054	2054
2055	2055	ret = ring->add_request(ring);
2056		- if (ret) {
2057		- kfree(request);
	2056	+ if (ret)
2058	2057	return ret;
2059		- }
2060	2058
2061	2059	request->seqno = intel_ring_get_seqno(ring);
2062	2060	request->ring = ring;
...	...	@@ -2095,6 +2093,7 @@
2095	2093
2096	2094	trace_i915_gem_request_add(ring, request->seqno);
2097	2095	ring->outstanding_lazy_seqno = 0;
	2096	+ ring->preallocated_lazy_request = NULL;
2098	2097
2099	2098	if (!dev_priv->ums.mm_suspended) {
2100	2099	i915_queue_hangcheck(ring->dev);
...	...	@@ -1498,6 +1498,16 @@
1498	1498	if (ring->outstanding_lazy_seqno)
1499	1499	return 0;
1500	1500
	1501	+ if (ring->preallocated_lazy_request == NULL) {
	1502	+ struct drm_i915_gem_request *request;
	1503	+
	1504	+ request = kmalloc(sizeof(*request), GFP_KERNEL);
	1505	+ if (request == NULL)
	1506	+ return -ENOMEM;
	1507	+
	1508	+ ring->preallocated_lazy_request = request;
	1509	+ }
	1510	+
1501	1511	return i915_gem_get_seqno(ring->dev, &ring->outstanding_lazy_seqno);
1502	1512	}
1503	1513
...	...	@@ -140,6 +140,7 @@
140	140	/**
141	141	* Do we have some not yet emitted requests outstanding?
142	142	*/
	143	+ struct drm_i915_gem_request *preallocated_lazy_request;
143	144	u32 outstanding_lazy_seqno;
144	145	bool gpu_caches_dirty;
145	146	bool fbc_dirty;