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Date: Mon, 17 Oct 2022 12:45:55 -0700 From: Jakub Kicinski <kuba@...nel.org> To: Joe Damato <jdamato@...tly.com> Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org, davem@...emloft.net, anthony.l.nguyen@...el.com, jesse.brandeburg@...el.com Subject: Re: [net-queue bugfix RFC] i40e: Clear IFF_RXFH_CONFIGURED when RSS is reset On Thu, 13 Oct 2022 15:54:31 -0700 Joe Damato wrote: > Before this change, reconfiguring the queue count using ethtool doesn't > always work, even for queue counts that were previously accepted because > the IFF_RXFH_CONFIGURED bit was not cleared when the flow indirection hash > is cleared by the driver. It's not cleared but when was it set? Could you describe the flow that gets us to this set a bit more? Normally clearing the IFF_RXFH_CONFIGURED in the driver is _only_ acceptable on error recovery paths, and should come with a "this should never happen" warning. > For example: > > $ sudo ethtool -x eth0 > RX flow hash indirection table for eth0 with 34 RX ring(s): > 0: 0 1 2 3 4 5 6 7 > 8: 8 9 10 11 12 13 14 15 > 16: 16 17 18 19 20 21 22 23 > 24: 24 25 26 27 28 29 30 31 > 32: 32 33 0 1 2 3 4 5 > [...snip...] > > As you can see, the flow indirection hash distributes flows to 34 queues. > > Increasing the number of queues from 34 to 64 works, and the flow > indirection hash is reset automatically: > > $ sudo ethtool -L eth0 combined 64 > $ sudo ethtool -x eth0 > RX flow hash indirection table for eth0 with 64 RX ring(s): > 0: 0 1 2 3 4 5 6 7 > 8: 8 9 10 11 12 13 14 15 > 16: 16 17 18 19 20 21 22 23 > 24: 24 25 26 27 28 29 30 31 > 32: 32 33 34 35 36 37 38 39 > 40: 40 41 42 43 44 45 46 47 > 48: 48 49 50 51 52 53 54 55 > 56: 56 57 58 59 60 61 62 63 This is odd, if IFF_RXFH_CONFIGURED is set driver should not re-initialize the indirection table. Which I believe is what you describe at the end of your message: > But, I can increase the queue count and the flow hash is preserved: > > $ sudo ethtool -L eth0 combined 64 > $ sudo ethtool -x eth0 > RX flow hash indirection table for eth0 with 64 RX ring(s): > 0: 0 1 2 3 4 5 6 7 > 8: 8 9 10 11 12 13 14 15 > 16: 16 17 18 19 0 1 2 3
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