[RFC PATCH 06/13] drm/ttm: Add a shrinker and shrinker accounting

[Thomas Hellström]

Register a TTM shrinker.

Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_device.c |  1 +
 drivers/gpu/drm/ttm/ttm_tt.c     | 90 ++++++++++++++++++++++++++++++++
 include/drm/ttm/ttm_tt.h         |  2 +
 3 files changed, 93 insertions(+)

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index a50e452e5245..f53994fa8fda 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -54,6 +54,7 @@ static void ttm_global_release(void)
 	if (--ttm_glob_use_count > 0)
 		goto out;
 
+	ttm_tt_mgr_fini();
 	ttm_pool_mgr_fini();
 	debugfs_remove(ttm_debugfs_root);
 
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index 771e5f3c2fee..fbf42db8a211 100644
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -37,6 +37,7 @@
 #include <linux/module.h>
 #include <drm/drm_cache.h>
 #include <drm/ttm/ttm_bo.h>
+#include <drm/ttm/ttm_pool.h>
 #include <drm/ttm/ttm_tt.h>
 
 #include "ttm_module.h"
@@ -54,6 +55,11 @@ module_param_named(dma32_pages_limit, ttm_dma32_pages_limit, ulong, 0644);
 static atomic_long_t ttm_pages_allocated;
 static atomic_long_t ttm_dma32_pages_allocated;
 
+static long shrinkable_pages;
+static long purgeable_pages;
+static DEFINE_RWLOCK(shrinkable_lock);
+static struct shrinker mm_shrinker;
+
 static bool ttm_tt_shrinkable(const struct ttm_device *bdev,
 			      const struct ttm_tt *tt)
 {
@@ -69,6 +75,14 @@ static void ttm_tt_mod_allocated(bool dma32, long value)
 		atomic_long_add(value, &ttm_dma32_pages_allocated);
 }
 
+static void ttm_tt_mod_shrinkable_pages(long shrinkable, long purgeable)
+{
+	write_lock(&shrinkable_lock);
+	shrinkable_pages += shrinkable;
+	purgeable_pages += purgeable;
+	write_unlock(&shrinkable_lock);
+}
+
 /*
  * Allocates a ttm structure for the given BO.
  */
@@ -352,6 +366,9 @@ int ttm_tt_populate(struct ttm_device *bdev,
 		}
 	}
 
+	if (ttm_tt_shrinkable(bdev, ttm))
+		ttm_tt_mod_shrinkable_pages(ttm->num_pages, 0);
+
 	return 0;
 
 error:
@@ -368,6 +385,9 @@ void ttm_tt_unpopulate(struct ttm_device *bdev, struct ttm_tt *ttm)
 	if (!ttm_tt_is_populated(ttm))
 		return;
 
+	if (ttm_tt_shrinkable(bdev, ttm))
+		ttm_tt_mod_shrinkable_pages(-(long)ttm->num_pages, 0);
+
 	if (bdev->funcs->ttm_tt_unpopulate)
 		bdev->funcs->ttm_tt_unpopulate(bdev, ttm);
 	else
@@ -394,6 +414,71 @@ DEFINE_SHOW_ATTRIBUTE(ttm_tt_debugfs_shrink);
 
 #endif
 
+static unsigned long ttm_tt_shrinker_count(struct shrinker *shrink,
+					   struct shrink_control *sc)
+{
+	unsigned long num_pages;
+
+	num_pages = get_nr_swap_pages();
+	read_lock(&shrinkable_lock);
+	num_pages = min_t(unsigned long, num_pages, shrinkable_pages);
+	num_pages += purgeable_pages;
+	read_unlock(&shrinkable_lock);
+
+	return num_pages ? num_pages : SHRINK_EMPTY;
+}
+
+static unsigned long ttm_tt_shrinker_scan(struct shrinker *shrink,
+					  struct shrink_control *sc)
+{
+	bool is_kswapd = current_is_kswapd();
+	struct ttm_operation_ctx ctx = {
+		.interruptible = false,
+		.no_wait_gpu = !is_kswapd,
+	};
+	unsigned long nr_to_scan, freed = 0;
+	long ret;
+
+	sc->nr_scanned = 0;
+	nr_to_scan = sc->nr_to_scan;
+
+	while (freed < nr_to_scan) {
+		ret = ttm_global_swapout(&ctx, TTM_SHRINK_PURGE);
+		if (ret <= 0)
+			break;
+
+		freed += ret;
+	}
+
+	sc->nr_scanned = freed;
+	if (freed < nr_to_scan)
+		nr_to_scan -= freed;
+	else
+		nr_to_scan = 0;
+	if (!nr_to_scan)
+		return freed ? freed : SHRINK_STOP;
+
+	while (freed < nr_to_scan) {
+		ret = ttm_global_swapout(&ctx, TTM_SHRINK_SWAP);
+		if (ret <= 0)
+			break;
+
+		freed += ret;
+	}
+
+	sc->nr_scanned = freed;
+
+	return freed ? freed : SHRINK_STOP;
+}
+
+void ttm_tt_mgr_fini(void)
+{
+	WARN_ON(atomic_long_read(&ttm_pages_allocated));
+	WARN_ON(atomic_long_read(&ttm_dma32_pages_allocated));
+	WARN_ON(shrinkable_pages);
+	WARN_ON(purgeable_pages);
+	unregister_shrinker(&mm_shrinker);
+}
 
 /*
  * ttm_tt_mgr_init - register with the MM shrinker
@@ -412,6 +497,11 @@ void ttm_tt_mgr_init(unsigned long num_pages, unsigned long num_dma32_pages)
 
 	if (!ttm_dma32_pages_limit)
 		ttm_dma32_pages_limit = num_dma32_pages;
+
+	mm_shrinker.count_objects = ttm_tt_shrinker_count;
+	mm_shrinker.scan_objects = ttm_tt_shrinker_scan;
+	mm_shrinker.seeks = DEFAULT_SEEKS;
+	(void)register_shrinker(&mm_shrinker, "ttm-objects");
 }
 
 static void ttm_kmap_iter_tt_map_local(struct ttm_kmap_iter *iter,
diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h
index 627168eba8f6..3f99787e2b93 100644
--- a/include/drm/ttm/ttm_tt.h
+++ b/include/drm/ttm/ttm_tt.h
@@ -221,6 +221,8 @@ static inline void ttm_tt_mark_for_clear(struct ttm_tt *ttm)
 
 void ttm_tt_mgr_init(unsigned long num_pages, unsigned long num_dma32_pages);
 
+void ttm_tt_mgr_fini(void);
+
 struct ttm_kmap_iter *ttm_kmap_iter_tt_init(struct ttm_kmap_iter_tt *iter_tt,
 					    struct ttm_tt *tt);
 
-- 
2.34.1