drm/ttm: check if free mem space is under the lower limit

the free mem space and the lower limit both include two parts:
system memory and swap space.

For the OOM triggered by TTM, that is the case as below:
first swap space is full of swapped out pages and soon
system memory also is filled up with ttm pages. and then
any memory allocation request will run into OOM.

to cover two cases:
a. if no swap disk at all or free swap space is under swap mem
   limit but available system mem is bigger than sys mem limit,
   allow TTM allocation;

b. if the available system mem is less than sys mem limit but
   free swap space is bigger than swap mem limit, allow TTM
   allocation.

v2: merge two memory limit(swap and system) into one
v3: keep original behavior except ttm_opt_ctx->flags with
    TTM_OPT_FLAG_FORCE_ALLOC
v4: always set force_alloc as tx->flags & TTM_OPT_FLAG_FORCE_ALLOC
v5: add an attribute for lower_mem_limit
v6: set lower_mem_limit as 0 to keep original behavior

Signed-off-by: Roger He <Hongbo.He@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/drm/ttm/ttm_memory.h b/include/drm/ttm/ttm_memory.h
index 8936285b6543..737b5fed8003 100644
--- a/include/drm/ttm/ttm_memory.h
+++ b/include/drm/ttm/ttm_memory.h
@@ -49,6 +49,8 @@
  * @work: The workqueue callback for the shrink queue.
  * @lock: Lock to protect the @shrink - and the memory accounting members,
  * that is, essentially the whole structure with some exceptions.
+ * @lower_mem_limit: include lower limit of swap space and lower limit of
+ * system memory.
  * @zones: Array of pointers to accounting zones.
  * @num_zones: Number of populated entries in the @zones array.
  * @zone_kernel: Pointer to the kernel zone.
@@ -67,6 +69,7 @@ struct ttm_mem_global {
 	struct workqueue_struct *swap_queue;
 	struct work_struct work;
 	spinlock_t lock;
+	uint64_t lower_mem_limit;
 	struct ttm_mem_zone *zones[TTM_MEM_MAX_ZONES];
 	unsigned int num_zones;
 	struct ttm_mem_zone *zone_kernel;
@@ -90,4 +93,6 @@ extern void ttm_mem_global_free_page(struct ttm_mem_global *glob,
 				     struct page *page, uint64_t size);
 extern size_t ttm_round_pot(size_t size);
 extern uint64_t ttm_get_kernel_zone_memory_size(struct ttm_mem_global *glob);
+extern bool ttm_check_under_lowerlimit(struct ttm_mem_global *glob,
+			uint64_t num_pages, struct ttm_operation_ctx *ctx);
 #endif