linux-kernel - [PATCH 8/8] drm/msm: Support evicting GEM objects to swap

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Date:   Mon,  5 Apr 2021 10:45:31 -0700
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Jordan Crouse <jordan@...micpenguin.net>,
        Rob Clark <robdclark@...omium.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        linux-arm-msm@...r.kernel.org (open list:DRM DRIVER FOR MSM ADRENO GPU),
        freedreno@...ts.freedesktop.org (open list:DRM DRIVER FOR MSM ADRENO
        GPU), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 8/8] drm/msm: Support evicting GEM objects to swap

From: Rob Clark <robdclark@...omium.org>

Now that tracking is wired up for potentially evictable GEM objects,
wire up shrinker and the remaining GEM bits for unpinning backing pages
of inactive objects.

Signed-off-by: Rob Clark <robdclark@...omium.org>
---
 drivers/gpu/drm/msm/msm_gem.c          | 23 ++++++++++++++++
 drivers/gpu/drm/msm/msm_gem_shrinker.c | 37 +++++++++++++++++++++++++-
 drivers/gpu/drm/msm/msm_gpu_trace.h    | 13 +++++++++
 3 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 163a1d30b5c9..2b731cf42294 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -759,6 +759,29 @@ void msm_gem_purge(struct drm_gem_object *obj)
 			0, (loff_t)-1);
 }
 
+/**
+ * Unpin the backing pages and make them available to be swapped out.
+ */
+void msm_gem_evict(struct drm_gem_object *obj)
+{
+	struct drm_device *dev = obj->dev;
+	struct msm_gem_object *msm_obj = to_msm_bo(obj);
+
+	GEM_WARN_ON(!msm_gem_is_locked(obj));
+	GEM_WARN_ON(is_unevictable(msm_obj));
+	GEM_WARN_ON(!msm_obj->evictable);
+	GEM_WARN_ON(msm_obj->active_count);
+
+	/* Get rid of any iommu mapping(s): */
+	put_iova_spaces(obj, false);
+
+	drm_vma_node_unmap(&obj->vma_node, dev->anon_inode->i_mapping);
+
+	put_pages(obj);
+
+	update_inactive(msm_obj);
+}
+
 void msm_gem_vunmap(struct drm_gem_object *obj)
 {
 	struct msm_gem_object *msm_obj = to_msm_bo(obj);
diff --git a/drivers/gpu/drm/msm/msm_gem_shrinker.c b/drivers/gpu/drm/msm/msm_gem_shrinker.c
index 38bf919f8508..52828028b9d4 100644
--- a/drivers/gpu/drm/msm/msm_gem_shrinker.c
+++ b/drivers/gpu/drm/msm/msm_gem_shrinker.c
@@ -9,12 +9,26 @@
 #include "msm_gpu.h"
 #include "msm_gpu_trace.h"
 
+bool enable_swap = true;
+MODULE_PARM_DESC(enable_swap, "Enable swappable GEM buffers");
+module_param(enable_swap, bool, 0600);
+
+static bool can_swap(void)
+{
+	return enable_swap && get_nr_swap_pages() > 0;
+}
+
 static unsigned long
 msm_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
 {
 	struct msm_drm_private *priv =
 		container_of(shrinker, struct msm_drm_private, shrinker);
-	return priv->shrinkable_count;
+	unsigned count = priv->shrinkable_count;
+
+	if (can_swap())
+		count += priv->evictable_count;
+
+	return count;
 }
 
 static bool
@@ -32,6 +46,17 @@ purge(struct msm_gem_object *msm_obj)
 	return true;
 }
 
+static bool
+evict(struct msm_gem_object *msm_obj)
+{
+	if (is_unevictable(msm_obj))
+		return false;
+
+	msm_gem_evict(&msm_obj->base);
+
+	return true;
+}
+
 static unsigned long
 scan(struct msm_drm_private *priv, unsigned nr_to_scan, struct list_head *list,
 		bool (*shrink)(struct msm_gem_object *msm_obj))
@@ -104,6 +129,16 @@ msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 	if (freed > 0)
 		trace_msm_gem_purge(freed << PAGE_SHIFT);
 
+	if (can_swap() && freed < sc->nr_to_scan) {
+		int evicted = scan(priv, sc->nr_to_scan - freed,
+				&priv->inactive_willneed, evict);
+
+		if (evicted > 0)
+			trace_msm_gem_evict(evicted << PAGE_SHIFT);
+
+		freed += evicted;
+	}
+
 	return (freed > 0) ? freed : SHRINK_STOP;
 }
 
diff --git a/drivers/gpu/drm/msm/msm_gpu_trace.h b/drivers/gpu/drm/msm/msm_gpu_trace.h
index 03e0c2536b94..ca0b08d7875b 100644
--- a/drivers/gpu/drm/msm/msm_gpu_trace.h
+++ b/drivers/gpu/drm/msm/msm_gpu_trace.h
@@ -128,6 +128,19 @@ TRACE_EVENT(msm_gem_purge,
 );
 
 
+TRACE_EVENT(msm_gem_evict,
+		TP_PROTO(u32 bytes),
+		TP_ARGS(bytes),
+		TP_STRUCT__entry(
+			__field(u32, bytes)
+			),
+		TP_fast_assign(
+			__entry->bytes = bytes;
+			),
+		TP_printk("Evicting %u bytes", __entry->bytes)
+);
+
+
 TRACE_EVENT(msm_gem_purge_vmaps,
 		TP_PROTO(u32 unmapped),
 		TP_ARGS(unmapped),
-- 
2.30.2