Subject: Re: [PATCH bpf-next v2 2/2] selftests/xsk: Enhance batch size support with dynamic configurations

From: Maciej Fijalkowski <[email-masked]>
Date: Mon, 1 Jul 2024 18:40:52 +0200

On Thu, Jun 27, 2024 at 04:35:48AM +0000, Tushar Vyavahare wrote:
> Introduce dynamic adjustment capabilities for fill_size and comp_size
> parameters to support larger batch sizes beyond the previous 2K limit.
> 
> Update HW_SW_MAX_RING_SIZE test cases to evaluate AF_XDP's robustness by
> pushing hardware and software ring sizes to their limits. This test
> ensures AF_XDP's reliability amidst potential producer/consumer throttling
> due to maximum ring utilization.
> 
> Signed-off-by: Tushar Vyavahare <[email-masked]>

Reviewed-by: Maciej Fijalkowski <[email-masked]>

> ---
>  tools/testing/selftests/bpf/xskxceiver.c | 26 ++++++++++++++++++------
>  tools/testing/selftests/bpf/xskxceiver.h |  2 ++
>  2 files changed, 22 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/xskxceiver.c b/tools/testing/selftests/bpf/xskxceiver.c
> index 088df53869e8..8144fd145237 100644
> --- a/tools/testing/selftests/bpf/xskxceiver.c
> +++ b/tools/testing/selftests/bpf/xskxceiver.c
> @@ -196,6 +196,12 @@ static int xsk_configure_umem(struct ifobject *ifobj, struct xsk_umem_info *umem
>  	};
>  	int ret;
>  
> +	if (umem->fill_size)
> +		cfg.fill_size = umem->fill_size;
> +
> +	if (umem->comp_size)
> +		cfg.comp_size = umem->comp_size;
> +
>  	if (umem->unaligned_mode)
>  		cfg.flags |= XDP_UMEM_UNALIGNED_CHUNK_FLAG;
>  
> @@ -265,6 +271,10 @@ static int __xsk_configure_socket(struct xsk_socket_info *xsk, struct xsk_umem_i
>  		cfg.bind_flags |= XDP_SHARED_UMEM;
>  	if (ifobject->mtu > MAX_ETH_PKT_SIZE)
>  		cfg.bind_flags |= XDP_USE_SG;
> +	if (umem->comp_size)
> +		cfg.tx_size = umem->comp_size;
> +	if (umem->fill_size)
> +		cfg.rx_size = umem->fill_size;
>  
>  	txr = ifobject->tx_on ? &xsk->tx : NULL;
>  	rxr = ifobject->rx_on ? &xsk->rx : NULL;
> @@ -1616,7 +1626,7 @@ static void xsk_populate_fill_ring(struct xsk_umem_info *umem, struct pkt_stream
>  	if (umem->num_frames < XSK_RING_PROD__DEFAULT_NUM_DESCS)
>  		buffers_to_fill = umem->num_frames;
>  	else
> -		buffers_to_fill = XSK_RING_PROD__DEFAULT_NUM_DESCS;
> +		buffers_to_fill = umem->fill_size;
>  
>  	ret = xsk_ring_prod__reserve(&umem->fq, buffers_to_fill, &idx);
>  	if (ret != buffers_to_fill)
> @@ -2445,7 +2455,7 @@ static int testapp_hw_sw_min_ring_size(struct test_spec *test)
>  
>  static int testapp_hw_sw_max_ring_size(struct test_spec *test)
>  {
> -	u32 max_descs = XSK_RING_PROD__DEFAULT_NUM_DESCS * 2;
> +	u32 max_descs = XSK_RING_PROD__DEFAULT_NUM_DESCS * 4;
>  	int ret;
>  
>  	test->set_ring = true;
> @@ -2453,7 +2463,8 @@ static int testapp_hw_sw_max_ring_size(struct test_spec *test)
>  	test->ifobj_tx->ring.tx_pending = test->ifobj_tx->ring.tx_max_pending;
>  	test->ifobj_tx->ring.rx_pending  = test->ifobj_tx->ring.rx_max_pending;
>  	test->ifobj_rx->umem->num_frames = max_descs;
> -	test->ifobj_rx->xsk->rxqsize = max_descs;
> +	test->ifobj_rx->umem->fill_size = max_descs;
> +	test->ifobj_rx->umem->comp_size = max_descs;
>  	test->ifobj_tx->xsk->batch_size = XSK_RING_PROD__DEFAULT_NUM_DESCS;
>  	test->ifobj_rx->xsk->batch_size = XSK_RING_PROD__DEFAULT_NUM_DESCS;
>  
> @@ -2461,9 +2472,12 @@ static int testapp_hw_sw_max_ring_size(struct test_spec *test)
>  	if (ret)
>  		return ret;
>  
> -	/* Set batch_size to 4095 */
> -	test->ifobj_tx->xsk->batch_size = max_descs - 1;
> -	test->ifobj_rx->xsk->batch_size = max_descs - 1;
> +	/* Set batch_size to 8152 for testing, as the ice HW ignores the 3 lowest bits when
> +	 * updating the Rx HW tail register.
> +	 */

Minor comment here is that in future it would be nice to have this quirk
only when ice hw is actually used

> +	test->ifobj_tx->xsk->batch_size = test->ifobj_tx->ring.tx_max_pending - 8;
> +	test->ifobj_rx->xsk->batch_size = test->ifobj_tx->ring.tx_max_pending - 8;
> +	pkt_stream_replace(test, max_descs, MIN_PKT_SIZE);
>  	return testapp_validate_traffic(test);
>  }
>  
> diff --git a/tools/testing/selftests/bpf/xskxceiver.h b/tools/testing/selftests/bpf/xskxceiver.h
> index 906de5fab7a3..885c948c5d83 100644
> --- a/tools/testing/selftests/bpf/xskxceiver.h
> +++ b/tools/testing/selftests/bpf/xskxceiver.h
> @@ -80,6 +80,8 @@ struct xsk_umem_info {
>  	void *buffer;
>  	u32 frame_size;
>  	u32 base_addr;
> +	u32 fill_size;
> +	u32 comp_size;
>  	bool unaligned_mode;
>  };
>  
> -- 
> 2.34.1
> 
>