cxgbe netmap: Avoid too frequent flush of CIDX by the NIC
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Authored by bwicht_verisign.com on Nov 6 2018, 1:49 PM.

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Summary

By default, CIDX (consumer index) is flushed by the NIC after every
update. That means a PCI transaction for each TX packet. By setting the
threshold to 32, the amount of PCI traffic is significantly reduced.

Submitted by: Marc De La Gueronniere <mdelagueronniere@verisign.com>
MFC after: 1 week
Sponsored by: Verisign, Inc.

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Buildable 20660
Build 20075: arc lint + arc unit

Event Timeline

bwicht_verisign.com created this revision.Nov 6 2018, 1:49 PM

Herald added a subscriber: ae. · View Herald TranscriptNov 6 2018, 1:49 PM

Harbormaster completed remote builds in B20660: Diff 50073.Nov 6 2018, 1:49 PM

lazy_tx_credit_flush in the driver is supposed to avoid the situation you described. Try setting it to 1 if it isn't already and see if that helps.

jch added a subscriber: jch.Nov 6 2018, 9:29 PM

In D17870#381915, @np wrote:

lazy_tx_credit_flush in the driver is supposed to avoid the situation you described. Try setting it to 1 if it isn't already and see if that helps.

In fact, we are using lazy_tx_credit_flush=1

Does this change have no impact when lazy_tx_credit_flush is used?

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sys/

dev/

cxgbe/

t4_netmap.c

1 line

Diff 50073

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cxgbe netmap: Avoid too frequent flush of CIDX by the NICNeeds ReviewPublicActions