netdev - RE: [Intel-wired-lan] [PATCH net v2 2/2] ixgbe: Enable setting RSS table to default values

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Date:   Thu, 20 Apr 2023 16:39:52 +0000
From:   "Pucha, HimasekharX Reddy" <himasekharx.reddy.pucha@...el.com>
To:     Joe Damato <jdamato@...tly.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        "kuba@...nel.org" <kuba@...nel.org>
Subject: RE: [Intel-wired-lan] [PATCH net v2 2/2] ixgbe: Enable setting RSS
 table to default values

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf Of Joe Damato
> Sent: Monday, April 17, 2023 10:29 AM
> To: intel-wired-lan@...ts.osuosl.org
> Cc: netdev@...r.kernel.org; Nguyen, Anthony L <anthony.l.nguyen@...el.com>; Brandeburg, Jesse <jesse.brandeburg@...el.com>; kuba@...nel.org
> Subject: Re: [Intel-wired-lan] [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(-)
> 

Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@...el.com> (A Contingent worker at Intel)