diff mbox series

[net-next,v3,3/7] iommu/dma: avoid expensive indirect calls for sync operations

Message ID 20240214162201.4168778-4-aleksander.lobakin@intel.com
State New
Headers
Series dma: skip calling no-op sync ops when possible |

Commit Message

Alexander Lobakin Feb. 14, 2024, 4:21 p.m. UTC 
  When IOMMU is on, the actual synchronization happens in the same cases
as with the direct DMA. Advertise %DMA_F_CAN_SKIP_SYNC in IOMMU DMA to
skip sync ops calls (indirect) for non-SWIOTLB buffers.

perf profile before the patch:

    18.53%  [kernel]       [k] gq_rx_skb
    14.77%  [kernel]       [k] napi_reuse_skb
     8.95%  [kernel]       [k] skb_release_data
     5.42%  [kernel]       [k] dev_gro_receive
     5.37%  [kernel]       [k] memcpy
<*>  5.26%  [kernel]       [k] iommu_dma_sync_sg_for_cpu
     4.78%  [kernel]       [k] tcp_gro_receive
<*>  4.42%  [kernel]       [k] iommu_dma_sync_sg_for_device
     4.12%  [kernel]       [k] ipv6_gro_receive
     3.65%  [kernel]       [k] gq_pool_get
     3.25%  [kernel]       [k] skb_gro_receive
     2.07%  [kernel]       [k] napi_gro_frags
     1.98%  [kernel]       [k] tcp6_gro_receive
     1.27%  [kernel]       [k] gq_rx_prep_buffers
     1.18%  [kernel]       [k] gq_rx_napi_handler
     0.99%  [kernel]       [k] csum_partial
     0.74%  [kernel]       [k] csum_ipv6_magic
     0.72%  [kernel]       [k] free_pcp_prepare
     0.60%  [kernel]       [k] __napi_poll
     0.58%  [kernel]       [k] net_rx_action
     0.56%  [kernel]       [k] read_tsc
<*>  0.50%  [kernel]       [k] __x86_indirect_thunk_r11
     0.45%  [kernel]       [k] memset

After patch, lines with <*> no longer show up, and overall
cpu usage looks much better (~60% instead of ~72%):

    25.56%  [kernel]       [k] gq_rx_skb
     9.90%  [kernel]       [k] napi_reuse_skb
     7.39%  [kernel]       [k] dev_gro_receive
     6.78%  [kernel]       [k] memcpy
     6.53%  [kernel]       [k] skb_release_data
     6.39%  [kernel]       [k] tcp_gro_receive
     5.71%  [kernel]       [k] ipv6_gro_receive
     4.35%  [kernel]       [k] napi_gro_frags
     4.34%  [kernel]       [k] skb_gro_receive
     3.50%  [kernel]       [k] gq_pool_get
     3.08%  [kernel]       [k] gq_rx_napi_handler
     2.35%  [kernel]       [k] tcp6_gro_receive
     2.06%  [kernel]       [k] gq_rx_prep_buffers
     1.32%  [kernel]       [k] csum_partial
     0.93%  [kernel]       [k] csum_ipv6_magic
     0.65%  [kernel]       [k] net_rx_action

iavf yields +10% of Mpps on Rx. This also unblocks batched allocations
of XSk buffers when IOMMU is active.

Co-developed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 drivers/iommu/dma-iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Robin Murphy Feb. 14, 2024, 5:58 p.m. UTC | #1 
On 2024-02-14 4:21 pm, Alexander Lobakin wrote:
> When IOMMU is on, the actual synchronization happens in the same cases
> as with the direct DMA. Advertise %DMA_F_CAN_SKIP_SYNC in IOMMU DMA to
> skip sync ops calls (indirect) for non-SWIOTLB buffers.
> 
> perf profile before the patch:
> 
>      18.53%  [kernel]       [k] gq_rx_skb
>      14.77%  [kernel]       [k] napi_reuse_skb
>       8.95%  [kernel]       [k] skb_release_data
>       5.42%  [kernel]       [k] dev_gro_receive
>       5.37%  [kernel]       [k] memcpy
> <*>  5.26%  [kernel]       [k] iommu_dma_sync_sg_for_cpu
>       4.78%  [kernel]       [k] tcp_gro_receive
> <*>  4.42%  [kernel]       [k] iommu_dma_sync_sg_for_device
>       4.12%  [kernel]       [k] ipv6_gro_receive
>       3.65%  [kernel]       [k] gq_pool_get
>       3.25%  [kernel]       [k] skb_gro_receive
>       2.07%  [kernel]       [k] napi_gro_frags
>       1.98%  [kernel]       [k] tcp6_gro_receive
>       1.27%  [kernel]       [k] gq_rx_prep_buffers
>       1.18%  [kernel]       [k] gq_rx_napi_handler
>       0.99%  [kernel]       [k] csum_partial
>       0.74%  [kernel]       [k] csum_ipv6_magic
>       0.72%  [kernel]       [k] free_pcp_prepare
>       0.60%  [kernel]       [k] __napi_poll
>       0.58%  [kernel]       [k] net_rx_action
>       0.56%  [kernel]       [k] read_tsc
> <*>  0.50%  [kernel]       [k] __x86_indirect_thunk_r11
>       0.45%  [kernel]       [k] memset
> 
> After patch, lines with <*> no longer show up, and overall
> cpu usage looks much better (~60% instead of ~72%):
> 
>      25.56%  [kernel]       [k] gq_rx_skb
>       9.90%  [kernel]       [k] napi_reuse_skb
>       7.39%  [kernel]       [k] dev_gro_receive
>       6.78%  [kernel]       [k] memcpy
>       6.53%  [kernel]       [k] skb_release_data
>       6.39%  [kernel]       [k] tcp_gro_receive
>       5.71%  [kernel]       [k] ipv6_gro_receive
>       4.35%  [kernel]       [k] napi_gro_frags
>       4.34%  [kernel]       [k] skb_gro_receive
>       3.50%  [kernel]       [k] gq_pool_get
>       3.08%  [kernel]       [k] gq_rx_napi_handler
>       2.35%  [kernel]       [k] tcp6_gro_receive
>       2.06%  [kernel]       [k] gq_rx_prep_buffers
>       1.32%  [kernel]       [k] csum_partial
>       0.93%  [kernel]       [k] csum_ipv6_magic
>       0.65%  [kernel]       [k] net_rx_action
> 
> iavf yields +10% of Mpps on Rx. This also unblocks batched allocations
> of XSk buffers when IOMMU is active.

Acked-by: Robin Murphy <robin.murphy@arm.com>

> Co-developed-by: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
> ---
>   drivers/iommu/dma-iommu.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 50ccc4f1ef81..4ab9ac13d362 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -1707,7 +1707,8 @@ static size_t iommu_dma_opt_mapping_size(void)
>   }
>   
>   static const struct dma_map_ops iommu_dma_ops = {
> -	.flags			= DMA_F_PCI_P2PDMA_SUPPORTED,
> +	.flags			= DMA_F_PCI_P2PDMA_SUPPORTED |
> +				  DMA_F_CAN_SKIP_SYNC,
>   	.alloc			= iommu_dma_alloc,
>   	.free			= iommu_dma_free,
>   	.alloc_pages		= dma_common_alloc_pages,
diff mbox series

Patch

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 50ccc4f1ef81..4ab9ac13d362 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1707,7 +1707,8 @@  static size_t iommu_dma_opt_mapping_size(void)
 }
 
 static const struct dma_map_ops iommu_dma_ops = {
-	.flags			= DMA_F_PCI_P2PDMA_SUPPORTED,
+	.flags			= DMA_F_PCI_P2PDMA_SUPPORTED |
+				  DMA_F_CAN_SKIP_SYNC,
 	.alloc			= iommu_dma_alloc,
 	.free			= iommu_dma_free,
 	.alloc_pages		= dma_common_alloc_pages,