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Date: Sun, 16 Apr 2023 21:58:48 -0700
From: Joe Damato <jdamato@...tly.com>
To: intel-wired-lan@...ts.osuosl.org
Cc: netdev@...r.kernel.org, jesse.brandeburg@...el.com,
anthony.l.nguyen@...el.com, kuba@...nel.org,
sridhar.samudrala@...el.com
Subject: Re: [PATCH net v2 2/2] ixgbe: Enable setting RSS table to default
values
On Sun, Apr 16, 2023 at 07:12:23PM +0000, Joe Damato wrote:
> ethtool uses `ETHTOOL_GRXRINGS` to compute how many queues are supported
> by RSS. The driver should return the smaller of either:
> - The maximum number of RSS queues the device supports, OR
> - The number of RX queues configured
>
> Prior to this change, running `ethtool -X $iface default` fails if the
> number of queues configured is larger than the number supported by RSS,
> even though changing the queue count correctly resets the flowhash to
> use all supported queues.
>
> Other drivers (for example, i40e) will succeed but the flow hash will
> reset to support the maximum number of queues supported by RSS, even if
> that amount is smaller than the configured amount.
>
> Prior to this change:
>
> $ sudo ethtool -L eth1 combined 20
> $ sudo ethtool -x eth1
> RX flow hash indirection table for eth1 with 20 RX ring(s):
> 0: 0 1 2 3 4 5 6 7
> 8: 8 9 10 11 12 13 14 15
> 16: 0 1 2 3 4 5 6 7
> 24: 8 9 10 11 12 13 14 15
> 32: 0 1 2 3 4 5 6 7
> ...
>
> You can see that the flowhash was correctly set to use the maximum
> number of queues supported by the driver (16).
>
> However, asking the NIC to reset to "default" fails:
>
> $ sudo ethtool -X eth1 default
> Cannot set RX flow hash configuration: Invalid argument
>
> After this change, the flowhash can be reset to default which will use
> all of the available RSS queues (16) or the configured queue count,
> whichever is smaller.
>
> Starting with eth1 which has 10 queues and a flowhash distributing to
> all 10 queues:
>
> $ sudo ethtool -x eth1
> RX flow hash indirection table for eth1 with 10 RX ring(s):
> 0: 0 1 2 3 4 5 6 7
> 8: 8 9 0 1 2 3 4 5
> 16: 6 7 8 9 0 1 2 3
> ...
>
> Increasing the queue count to 48 resets the flowhash to distribute to 16
> queues, as it did before this patch:
>
> $ sudo ethtool -L eth1 combined 48
> $ sudo ethtool -x eth1
> RX flow hash indirection table for eth1 with 16 RX ring(s):
> 0: 0 1 2 3 4 5 6 7
> 8: 8 9 10 11 12 13 14 15
> 16: 0 1 2 3 4 5 6 7
> ...
>
> Due to the other bugfix in this series, the flowhash can be set to use
> queues 0-5:
>
> $ sudo ethtool -X eth1 equal 5
> $ sudo ethtool -x eth1
> RX flow hash indirection table for eth1 with 16 RX ring(s):
> 0: 0 1 2 3 4 0 1 2
> 8: 3 4 0 1 2 3 4 0
> 16: 1 2 3 4 0 1 2 3
> ...
>
> Due to this bugfix, the flowhash can be reset to default and use 16
> queues:
>
> $ sudo ethtool -X eth1 default
> $ sudo ethtool -x eth1
> RX flow hash indirection table for eth1 with 16 RX ring(s):
> 0: 0 1 2 3 4 5 6 7
> 8: 8 9 10 11 12 13 14 15
> 16: 0 1 2 3 4 5 6 7
> ...
Fixes: 91cd94bfe4f0 ("ixgbe: add basic support for setting and getting nfc
controls")
> Signed-off-by: Joe Damato <jdamato@...tly.com>
> Reviewed-by: Sridhar Samudrala <sridhar.samudrala@...el.com>
> ---
> .../net/ethernet/intel/ixgbe/ixgbe_ethtool.c | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
> index 821dfd323fa9..0bbad4a5cc2f 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
> @@ -2665,6 +2665,14 @@ static int ixgbe_get_rss_hash_opts(struct ixgbe_adapter *adapter,
> return 0;
> }
>
> +static int ixgbe_rss_indir_tbl_max(struct ixgbe_adapter *adapter)
> +{
> + if (adapter->hw.mac.type < ixgbe_mac_X550)
> + return 16;
> + else
> + return 64;
> +}
> +
> static int ixgbe_get_rxnfc(struct net_device *dev, struct ethtool_rxnfc *cmd,
> u32 *rule_locs)
> {
> @@ -2673,7 +2681,8 @@ static int ixgbe_get_rxnfc(struct net_device *dev, struct ethtool_rxnfc *cmd,
>
> switch (cmd->cmd) {
> case ETHTOOL_GRXRINGS:
> - cmd->data = adapter->num_rx_queues;
> + cmd->data = min_t(int, adapter->num_rx_queues,
> + ixgbe_rss_indir_tbl_max(adapter));
> ret = 0;
> break;
> case ETHTOOL_GRXCLSRLCNT:
> @@ -3075,14 +3084,6 @@ static int ixgbe_set_rxnfc(struct net_device *dev, struct ethtool_rxnfc *cmd)
> return ret;
> }
>
> -static int ixgbe_rss_indir_tbl_max(struct ixgbe_adapter *adapter)
> -{
> - if (adapter->hw.mac.type < ixgbe_mac_X550)
> - return 16;
> - else
> - return 64;
> -}
> -
> static u32 ixgbe_get_rxfh_key_size(struct net_device *netdev)
> {
> return IXGBE_RSS_KEY_SIZE;
> --
> 2.25.1
>
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