Re: [PATCH 5.15 042/136] ice: xsk: Force rings to be sized to power of 2

Maciej Fijalkowski
2022-08-29T11:37:27Z

On Mon, Aug 29, 2022 at 12:58:29PM +0200, Greg Kroah-Hartman wrote:
> From: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
>
> [ Upstream commit 296f13ff3854535009a185aaf8e3603266d39d94 ]
>
> With the upcoming introduction of batching to XSK data path,
> performance wise it will be the best to have the ring descriptor count
> to be aligned to power of 2.
>
> Check if ring sizes that user is going to attach the XSK socket fulfill
> the condition above. For Tx side, although check is being done against
> the Tx queue and in the end the socket will be attached to the XDP
> queue, it is fine since XDP queues get the ring->count setting from Tx
> queues.

Hi Greg,

We had multiple customers reporting that this change makes them unable to
use max ring size which is 8160 for this particular driver (which is not a
power of 2 obviously) so we are about to send a patch that will drop this
limitation.

To avoid the double work, can you please not proceed with this one?
The other two:
ice: xsk: prohibit usage of non-balanced queue id
ice: xsk: use Rx rings XDP ring when picking NAPI context

are valid and needed.

FWIW this was a part of -next patch set, so I suppose you picked this due
to some dependency?

Thanks,
Maciej

>
> Suggested-by: Alexander Lobakin <alexandr.lobakin@intel.com>
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
> Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
> Link: https://lore.kernel.org/bpf/20220125160446.78976-3-maciej.fijalkowski@intel.com
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> drivers/net/ethernet/intel/ice/ice_xsk.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
> index 5581747947e57..0348cc4265034 100644
> --- a/drivers/net/ethernet/intel/ice/ice_xsk.c
> +++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
> @@ -321,6 +321,13 @@ int ice_xsk_pool_setup(struct ice_vsi *vsi, struct xsk_buff_pool *pool, u16 qid)
> bool if_running, pool_present = !!pool;
> int ret = 0, pool_failure = 0;
>
> + if (!is_power_of_2(vsi->rx_rings[qid]->count) ||
> + !is_power_of_2(vsi->tx_rings[qid]->count)) {
> + netdev_err(vsi->netdev, "Please align ring sizes to power of 2\n");
> + pool_failure = -EINVAL;
> + goto failure;
> + }
> +
> if_running = netif_running(vsi->netdev) && ice_is_xdp_ena_vsi(vsi);
>
> if (if_running) {
> @@ -343,6 +350,7 @@ int ice_xsk_pool_setup(struct ice_vsi *vsi, struct xsk_buff_pool *pool, u16 qid)
> netdev_err(vsi->netdev, "ice_qp_ena error = %d\n", ret);
> }
>
> +failure:
> if (pool_failure) {
> netdev_err(vsi->netdev, "Could not %sable buffer pool, error = %d\n",
> pool_present ? "en" : "dis", pool_failure);
> --
> 2.35.1
>
>
>