[dpdk-dev] [PATCH v2 3/3] net/af_xdp: preferred busy polling
Ferruh Yigit
ferruh.yigit at intel.com
Tue Mar 9 17:33:10 CET 2021
On 3/9/2021 10:19 AM, Ciara Loftus wrote:
> This commit introduces support for preferred busy polling
> to the AF_XDP PMD. This feature aims to improve single-core
> performance for AF_XDP sockets under heavy load.
>
> A new vdev arg is introduced called 'busy_budget' whose default
> value is 64. busy_budget is the value supplied to the kernel
> with the SO_BUSY_POLL_BUDGET socket option and represents the
> busy-polling NAPI budget. To set the budget to a different value
> eg. 256:
>
> --vdev=net_af_xdp0,iface=eth0,busy_budget=256
>
> Preferred busy polling is enabled by default provided a kernel with
> version >= v5.11 is in use. To disable it, set the budget to zero.
>
> The following settings are also strongly recommended to be used in
> conjunction with this feature:
>
> echo 2 | sudo tee /sys/class/net/eth0/napi_defer_hard_irqs
> echo 200000 | sudo tee /sys/class/net/eth0/gro_flush_timeout
>
> .. where eth0 is the interface being used by the PMD.
>
> Signed-off-by: Ciara Loftus <ciara.loftus at intel.com>
<...>
> --- a/doc/guides/rel_notes/release_21_05.rst
> +++ b/doc/guides/rel_notes/release_21_05.rst
> @@ -70,6 +70,10 @@ New Features
> * Added command to display Rx queue used descriptor count.
> ``show port (port_id) rxq (queue_id) desc used count``
>
> +* **Updated the AF_XDP driver.**
> +
> + * Added support for preferred busy polling.
> +
>
Can you please move the update after above the testpmd updates?
For more details the expected order is in the section comment.
> +static int
> +configure_preferred_busy_poll(struct pkt_rx_queue *rxq)
> +{
> + int sock_opt = 1;
> + int fd = xsk_socket__fd(rxq->xsk);
> + int ret = 0;
> +
> + ret = setsockopt(fd, SOL_SOCKET, SO_PREFER_BUSY_POLL,
> + (void *)&sock_opt, sizeof(sock_opt));
> + if (ret < 0) {
> + AF_XDP_LOG(DEBUG, "Failed to set SO_PREFER_BUSY_POLL\n");
> + goto err_prefer;
> + }
> +
> + sock_opt = ETH_AF_XDP_DFLT_BUSY_TIMEOUT;
> + ret = setsockopt(fd, SOL_SOCKET, SO_BUSY_POLL, (void *)&sock_opt,
> + sizeof(sock_opt));
> + if (ret < 0) {
> + AF_XDP_LOG(DEBUG, "Failed to set SO_BUSY_POLL\n");
[1]
> + goto err_timeout;
> + }
> +
> + sock_opt = rxq->busy_budget;
> + ret = setsockopt(fd, SOL_SOCKET, SO_BUSY_POLL_BUDGET,
> + (void *)&sock_opt, sizeof(sock_opt));
> + if (ret < 0) {
> + AF_XDP_LOG(DEBUG, "Failed to set SO_BUSY_POLL_BUDGET\n");
In above [1] and here, shouldn't the function return error, even the rollback is
successful.
I am thinking a case an invalid 'busy_budget' provided, like a very big number
or negative value.
> + } else {
> + AF_XDP_LOG(INFO, "Busy polling budget set to: %u\n",
> + rxq->busy_budget);
> + return 0;
> + }
> +
> + /* setsockopt failure - attempt to restore xsk to default state and
> + * proceed without busy polling support.
> + */
> + sock_opt = 0;
> + ret = setsockopt(fd, SOL_SOCKET, SO_BUSY_POLL, (void *)&sock_opt,
> + sizeof(sock_opt));
> + if (ret < 0) {
> + AF_XDP_LOG(ERR, "Failed to unset SO_BUSY_POLL\n");
> + return -1;
> + }
> +
> +err_timeout:
> + sock_opt = 0;
> + ret = setsockopt(fd, SOL_SOCKET, SO_PREFER_BUSY_POLL,
> + (void *)&sock_opt, sizeof(sock_opt));
> + if (ret < 0) {
> + AF_XDP_LOG(ERR, "Failed to unset SO_PREFER_BUSY_POLL\n");
> + return -1;
> + }
> +
> +err_prefer:
> + rxq->busy_budget = 0;
> + return 0;
> +}
> +
<...>
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