> Using order 4 pages would be helpful for many IOMMUs, but it could spend
> quite much time in page allocation perspective.
>
> The order 4 allocation with __GFP_RECLAIM may spend much time in
> reclaim and compation logic. __GFP_NORETRY also may affect. These cause
> unpredictable delay.
>
> To get reasonable allocation speed from dma-buf system heap, use
> HIGH_ORDER_GFP for order 4 to avoid reclaim.
>
> Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
> ---
> drivers/dma-buf/heaps/system_heap.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> index e8bd10e60998..5a405e99ef1e 100644
> --- a/drivers/dma-buf/heaps/system_heap.c
> +++ b/drivers/dma-buf/heaps/system_heap.c
> @@ -42,11 +42,10 @@ struct dma_heap_attachment {
> };
>
> #define LOW_ORDER_GFP (GFP_HIGHUSER | __GFP_ZERO | __GFP_COMP)
> -#define MID_ORDER_GFP (LOW_ORDER_GFP | __GFP_NOWARN)
> #define HIGH_ORDER_GFP (((GFP_HIGHUSER | __GFP_ZERO | __GFP_NOWARN \
> | __GFP_NORETRY) & ~__GFP_RECLAIM) \
> | __GFP_COMP)
> -static gfp_t order_flags[] = {HIGH_ORDER_GFP, MID_ORDER_GFP, LOW_ORDER_GFP};
> +static gfp_t order_flags[] = {HIGH_ORDER_GFP, HIGH_ORDER_GFP, LOW_ORDER_GFP};
> /*
> * The selection of the orders used for allocation (1MB, 64K, 4K) is designed
> * to match with the sizes often found in IOMMUs. Using order 4 pages instead
> --
> 2.17.1
added John Stultz <jstultz@xxxxxxxxxx>
