drm/ttm: improve uncached page deallocation.

Calls to set_memory_wb() incure heavy TLB flush and IPI cost. To
minimize those wait until pool grow beyond batch size before
draining the pool.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Reviewed-and-Tested-by: Michel Dänzer <michel@daenzer.net>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
index af23080..624d941 100644 (file)
--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
@@ -963,13 +963,13 @@ void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma, struct device *dev)
        } else {
                pool->npages_free += count;
                list_splice(&ttm_dma->pages_list, &pool->free_list);
-               if (pool->npages_free > _manager->options.max_size) {
+               /*
+                * Wait to have at at least NUM_PAGES_TO_ALLOC number of pages
+                * to free in order to minimize calls to set_memory_wb().
+                */
+               if (pool->npages_free >= (_manager->options.max_size +
+                                         NUM_PAGES_TO_ALLOC))
                        npages = pool->npages_free - _manager->options.max_size;
-                       /* free at least NUM_PAGES_TO_ALLOC number of pages
-                        * to reduce calls to set_memory_wb */
-                       if (npages < NUM_PAGES_TO_ALLOC)
-                               npages = NUM_PAGES_TO_ALLOC;
-               }
        }
        spin_unlock_irqrestore(&pool->lock, irq_flags);