OVS DPDK DMA-Dev library/Design Discussion

["Mcnamara, John" <john.mcnamara@intel.com>]

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This meeting is a follow-up to the previous calls in March and the discussion which has happened since on the DPDK and OVS mailing lists.

Three approaches were presented in the previous calls:

*       "Defer work": Handle DMA completions at OVS PMD thread level
*       "v3": Handle DMA Tx completions from Rx context.
*       "v3 + lockless ring": Handle DMA Tx completions from Rx context + lockless ring to avoid contention.

After these calls, the discussion continued on the DPDK and OVS mailing lists, where an alternate approach has been proposed.

The newly-suggested approach:

*       "DMA VirtQ Completions": Add an additional transaction(s) to each burst of DMA copies; a special transaction containing the memory write operation that makes the descriptors available to the Virtio driver. Also separate the actual kick of the guest with the data transfer.

Agenda for call 26th April:

*       Intel team will present slides to help understand the differences in architecture/designs.
*       Discuss the strengths/weaknesses/feasibility of the "DMA VirtQ Completions" approach, comparing to current best-candidate "Defer Work".
*       Work toward single-solution to be accepted upstream in DPDK and OVS

Google Meet link and slides to follow.




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ORGANIZER;CN="Mcnamara, John":mailto:john.mcnamara@intel.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN="Stokes, Ia
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ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN="Pai G, Sun
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ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN="Hu, Jiayu":
 mailto:jiayu.hu@intel.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN="Ferriter, 
 Cian":mailto:cian.ferriter@intel.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN="Van Haaren
 , Harry":mailto:harry.van.haaren@intel.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN=Ilya Maxim
 ets:mailto:i.maximets@ovn.org
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN=Maxime Coq
 uelin (maxime.coquelin@redhat.com):mailto:maxime.coquelin@redhat.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN=ovs-dev@op
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ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN=dev@dpdk.o
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ATTENDEE;ROLE=OPT-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN="O'Driscoll
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ATTENDEE;ROLE=OPT-PARTICIPANT;PARTSTAT=NEEDS-ACTION;RSVP=TRUE;CN="Finn, Emma"
 :mailto:emma.finn@intel.com
DESCRIPTION;LANGUAGE=en-US:This meeting is a follow-up to the previous call
 s in March and the discussion which has happened since on the DPDK and OVS
  mailing lists.\n\nThree approaches were presented in the previous calls:\
 n\n•       "Defer work": Handle DMA completions at OVS PMD thread level\
 n•       "v3": Handle DMA Tx completions from Rx context.\n•       "v3
  + lockless ring": Handle DMA Tx completions from Rx context + lockless ri
 ng to avoid contention.\n\nAfter these calls\, the discussion continued on
  the DPDK and OVS mailing lists\, where an alternate approach has been pro
 posed.\n\nThe newly-suggested approach:\n\n•       "DMA VirtQ Completion
 s": Add an additional transaction(s) to each burst of DMA copies\; a speci
 al transaction containing the memory write operation that makes the descri
 ptors available to the Virtio driver. Also separate the actual kick of the
  guest with the data transfer.\n\nAgenda for call 26th April:\n\n•      
  Intel team will present slides to help understand the differences in arch
 itecture/designs.\n•       Discuss the strengths/weaknesses/feasibility 
 of the "DMA VirtQ Completions" approach\, comparing to current best-candid
 ate "Defer Work".\n•       Work toward single-solution to be accepted up
 stream in DPDK and OVS\n\nGoogle Meet link and slides to follow.\n\n\n\n
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SUMMARY;LANGUAGE=en-US:OVS DPDK DMA-Dev library/Design Discussion
DTSTART;TZID=GMT Standard Time:20220426T140000
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