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Message-ID: <20230416190417.GA43280@fastly.com>
Date: Sun, 16 Apr 2023 12:04:18 -0700
From: Joe Damato <jdamato@...tly.com>
To: "Samudrala, Sridhar" <sridhar.samudrala@...el.com>
Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
jesse.brandeburg@...el.com, anthony.l.nguyen@...el.com,
kuba@...nel.org
Subject: Re: [PATCH net 2/2] ixgbe: Allow ixgbe to reset default flow hash
On Sun, Apr 16, 2023 at 10:29:36AM -0500, Samudrala, Sridhar wrote:
>
>
> On 4/15/2023 12:48 AM, 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
> >...
> >
> >Signed-off-by: Joe Damato <jdamato@...tly.com>
>
> Thanks for the detailed commit message and steps to reproduce
> and validate the issue.
No worries. Thanks for the review.
> Would suggest changing the title to indicate that this fix is enabling
> setting the RSS indirection table to default value.
OK, sure. I can send a v2 that includes your reviewed tags and changes the
title of this commit (but makes no other changes).
I'll make the new title of this commit ixgbe: Enable setting RSS table to
default values.
Hope that's ok; will send out the v2 shortly.
> 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;
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