Am 25.01.2018 um 10:59 schrieb Chunming Zhou:
there is a scheduling balance issue about get node like:
a. process A allocates full memory and use it for submission.
b. process B tries to allocates memory, will wait for process A BO idle in eviction.
c. process A completes the job, process B eviction will put process A BO node,
but in the meantime, process C is comming to allocate BO, whill directly get node successfully, and do submission,
process B will again wait for process C BO idle.
d. repeat the above setps, process B could be delayed much more.
NAK, this is intended behavior please don't change it. If you start to
use a per domain mutex like this no concurrent allocation is possible
any more.
In other words when process B needs a lot of memory and blocks for that
memory to be evicted it is intended that process C which doesn't needs
so much memory can jump in and execute before B.
add a mutex to gerantee the allocation sequence for same domain. But there is a possibility that
visible vram could be evicted to invisilbe, the tricky is they are same domain manager, so which needs a special handling.
To avoid lock inversion you would need a global mutex here, otherwise
you can run into the following issue:
Eviction: VRAM domain mutex locked first then GTT mutex.
Swapping in: GTT mutex locked first, then VRAM mutex.
Regards,
Christian.
Change-Id: I260e8eb704f7b4788b071d3f641f21b242912256
Signed-off-by: Chunming Zhou <david1.zhou@xxxxxxx>
---
drivers/gpu/drm/ttm/ttm_bo.c | 16 +++++++++++++++-
include/drm/ttm/ttm_bo_api.h | 2 ++
include/drm/ttm/ttm_bo_driver.h | 1 +
3 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index d33a6bb742a1..f465f1d38711 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -969,7 +969,11 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
if (mem_type == TTM_PL_SYSTEM)
break;
+ if (ctx->man != man)
+ mutex_lock(&man->node_mutex);
ret = (*man->func->get_node)(man, bo, place, mem);
+ if (ctx->man != man)
+ mutex_unlock(&man->node_mutex);
if (unlikely(ret))
return ret;
@@ -991,6 +995,7 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
for (i = 0; i < placement->num_busy_placement; ++i) {
const struct ttm_place *place = &placement->busy_placement[i];
+ struct ttm_operation_ctx busy_ctx;
ret = ttm_mem_type_from_place(place, &mem_type);
if (ret)
@@ -1018,7 +1023,15 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
return 0;
}
- ret = ttm_bo_mem_force_space(bo, mem_type, place, mem, ctx);
+ memcpy(&busy_ctx, ctx, sizeof(busy_ctx));
+ if (ctx->man != man) {
+ mutex_lock(&man->node_mutex);
+ busy_ctx.man = man;
+ }
+ ret = ttm_bo_mem_force_space(bo, mem_type, place, mem,
+ &busy_ctx);
+ if (ctx->man != man)
+ mutex_unlock(&man->node_mutex);
if (ret == 0 && mem->mm_node) {
mem->placement = cur_flags;
return 0;
@@ -1449,6 +1462,7 @@ int ttm_bo_init_mm(struct ttm_bo_device *bdev, unsigned type,
man->io_reserve_fastpath = true;
man->use_io_reserve_lru = false;
mutex_init(&man->io_reserve_mutex);
+ mutex_init(&man->node_mutex);
spin_lock_init(&man->move_lock);
INIT_LIST_HEAD(&man->io_reserve_lru);
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 2cd025c2abe7..b08629050215 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -265,6 +265,7 @@ struct ttm_bo_kmap_obj {
* @no_wait_gpu: Return immediately if the GPU is busy.
* @allow_reserved_eviction: Allow eviction of reserved BOs.
* @resv: Reservation object to allow reserved evictions with.
+ * @man: record ctx is under man->node_mutex.
*
* Context for TTM operations like changing buffer placement or general memory
* allocation.
@@ -275,6 +276,7 @@ struct ttm_operation_ctx {
bool allow_reserved_eviction;
struct reservation_object *resv;
uint64_t bytes_moved;
+ struct ttm_mem_type_manager *man;
};
/**
diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h
index 9b417eb2df20..d85d6ee4f54d 100644
--- a/include/drm/ttm/ttm_bo_driver.h
+++ b/include/drm/ttm/ttm_bo_driver.h
@@ -288,6 +288,7 @@ struct ttm_mem_type_manager {
uint32_t default_caching;
const struct ttm_mem_type_manager_func *func;
void *priv;
+ struct mutex node_mutex;
struct mutex io_reserve_mutex;
bool use_io_reserve_lru;
bool io_reserve_fastpath;
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