[PATCH] drm/ttm: add minimum residency constraint for bo eviction

[j.glisse@gmail.com]

From: Jerome Glisse <jglisse@redhat.com>

This patch add a minimum residency time configurable for each memory
pool (VRAM, GTT, ...). Intention is to avoid having a lot of memory
eviction from VRAM up to a point where the GPU pretty much spend all
it's time moving things in and out.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
---
 drivers/gpu/drm/radeon/radeon_ttm.c | 3 +++
 drivers/gpu/drm/ttm/ttm_bo.c        | 7 +++++++
 include/drm/ttm/ttm_bo_api.h        | 1 +
 include/drm/ttm/ttm_bo_driver.h     | 1 +
 4 files changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 5ebe1b3..88722c4 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -129,11 +129,13 @@ static int radeon_init_mem_type(struct ttm_bo_device *bdev, uint32_t type,
 	switch (type) {
 	case TTM_PL_SYSTEM:
 		/* System memory */
+		man->minimum_residency_time_ms = 0;
 		man->flags = TTM_MEMTYPE_FLAG_MAPPABLE;
 		man->available_caching = TTM_PL_MASK_CACHING;
 		man->default_caching = TTM_PL_FLAG_CACHED;
 		break;
 	case TTM_PL_TT:
+		man->minimum_residency_time_ms = 0;
 		man->func = &ttm_bo_manager_func;
 		man->gpu_offset = rdev->mc.gtt_start;
 		man->available_caching = TTM_PL_MASK_CACHING;
@@ -156,6 +158,7 @@ static int radeon_init_mem_type(struct ttm_bo_device *bdev, uint32_t type,
 		break;
 	case TTM_PL_VRAM:
 		/* "On-card" video ram */
+		man->minimum_residency_time_ms = 500;
 		man->func = &ttm_bo_manager_func;
 		man->gpu_offset = rdev->mc.vram_start;
 		man->flags = TTM_MEMTYPE_FLAG_FIXED |
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 39dcc58..40476121 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -452,6 +452,7 @@ moved:
 		bo->cur_placement = bo->mem.placement;
 	} else
 		bo->offset = 0;
+	bo->jiffies = jiffies;
 
 	return 0;
 
@@ -810,6 +811,12 @@ retry:
 	}
 
 	bo = list_first_entry(&man->lru, struct ttm_buffer_object, lru);
+
+	if (time_after(jiffies, bo->jiffies) && jiffies_to_msecs(jiffies - bo->jiffies) >= man->minimum_residency_time_ms) {
+		spin_unlock(&glob->lru_lock);
+		return -EBUSY;
+	}
+
 	kref_get(&bo->list_kref);
 
 	if (!list_empty(&bo->ddestroy)) {
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index e8028ad..9e12313 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -275,6 +275,7 @@ struct ttm_buffer_object {
 
 	unsigned long offset;
 	uint32_t cur_placement;
+	unsigned long jiffies;
 
 	struct sg_table *sg;
 };
diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
index d803b92..7f60a18e6 100644
--- a/include/drm/ttm/ttm_bo_driver.h
+++ b/include/drm/ttm/ttm_bo_driver.h
@@ -280,6 +280,7 @@ struct ttm_mem_type_manager {
 	struct mutex io_reserve_mutex;
 	bool use_io_reserve_lru;
 	bool io_reserve_fastpath;
+	unsigned long minimum_residency_time_ms;
 
 	/*
 	 * Protected by @io_reserve_mutex:
-- 
1.7.11.7