[PATCH 4/6] drm/ttm: add the infrastructur for pipelined evictions

[Thomas Hellstrom]

Christian,

Thanks for doing this!
A question below:

On 06/15/2016 01:44 PM, Christian König wrote:
> From: Christian König <christian.koenig at amd.com>
>
> Free up the memory immediately, remember the last eviction for each domain and
> make new allocations depend on the last eviction to be completed.
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> ---
>  drivers/gpu/drm/ttm/ttm_bo.c      | 49 ++++++++++++++++++---
>  drivers/gpu/drm/ttm/ttm_bo_util.c | 92 +++++++++++++++++++++++++++++++++++++++
>  include/drm/ttm/ttm_bo_driver.h   | 24 ++++++++++
>  3 files changed, 160 insertions(+), 5 deletions(-)
>
>
>  
>  	/*
>  	 * Protected by @io_reserve_mutex:
> @@ -298,6 +301,11 @@ struct ttm_mem_type_manager {
>  	 */
>  
>  	struct list_head lru;
> +
> +	/*
> +	 * Protected by @move_lock.
> +	 */
> +	struct fence *move;
>  };
>  

Did you look at protecting the move fence with RCU? I figure where there
actually is a fence it doesn't matter much but in the fastpath where
move is NULL we'd be able to get rid of a number of locking cycles.

I guess though there might be both licensing implications and
requirements to using kfree_rcu() to free the fence.

/Thomas