s390/qeth: balance the TX queue selection for IQD devices

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For ucast traffic, qeth_iqd_select_queue() falls back to
netdev_pick_tx(). This will potentially use skb_tx_hash() to distribute
the flow over all active TX queues - so txq 0 is a valid selection, and
qeth_iqd_select_queue() needs to check for this and put it on some other
queue. As a result, the distribution for ucast flows is unbalanced and
hits QETH_IQD_MIN_UCAST_TXQ heavier than the other queues.

Open-coding a custom variant of skb_tx_hash() isn't an option, since
netdev_pick_tx() also gives us eg. access to XPS. But we can pull a
little trick: add a single TC class that excludes the mcast txq, and
thus encourage skb_tx_hash() to not pick the mcast txq.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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Julian Wiedmann 2020-03-18 13:54:50 +01:00 • committed by David S. Miller

parent 66cddf1019

commit 5d8ce41c6a

3 changed files with 46 additions and 2 deletions

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1

drivers/s390/net/qeth_core.h

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45

drivers/s390/net/qeth_core_main.c

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2

drivers/s390/net/qeth_ethtool.c

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