Re: [dpdk-dev] [PATCH v5 0/2] app/testpmd: improve multiprocess support

[Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>]

On 30/09/2016 15:00, Marcin Kerlin wrote:
> This patch ensure not overwrite device data in the multiprocess application.
>
> 1)Changes in the library introduces continuity in array rte_eth_dev_data[]
> shared between all processes. Secondary process adds new entries in free
> space instead of overwriting existing entries.
>
> 2)Changes in application testpmd allow secondary process to attach the
> mempool created by primary process rather than create new and in the case of
> quit or force quit to free devices data from shared array rte_eth_dev_data[].
>
> -------------------------
> How to reproduce the bug:
>
> 1) Run primary process:
> ./testpmd -c 0xf -n 4 --socket-mem='512,0' -w 03:00.1 -w 03:00.0
> --proc-type=primary --file-prefix=xz1 -- -i
>
> (gdb) print rte_eth_devices[0].data.name
> $52 = "3:0.1"
> (gdb) print rte_eth_devices[1].data.name
> $53 = "3:0.0"
>
> 2) Run secondary process:
> ./testpmd -c 0xf0 --socket-mem='512,0' -n 4 -v -b 03:00.1 -b 03:00.0
> --vdev 'eth_pcap0,rx_pcap=/var/log/device1.pcap, tx_pcap=/var/log/device2.pcap'
> --proc-type=secondary --file-prefix=xz1 -- -i
>
> (gdb) print rte_eth_devices[0].data.name
> $52 = "eth_pcap0"
> (gdb) print rte_eth_devices[1].data.name
> $53 = "eth_pcap1"
>
> 3) Go back to the primary and re-check:
> (gdb) print rte_eth_devices[0].data.name
> $54 = "eth_pcap0"
> (gdb) print rte_eth_devices[1].data.name
> $55 = "eth_pcap1"
>
> It means that secondary process overwrite data of primary process.
>
> This patch fix it and now if we go back to the primary and re-check then
> everything is fine:
> (gdb) print rte_eth_devices[0].data.name
> $56 = "3:0.1"
> (gdb) print rte_eth_devices[1].data.name
> $57 = "3:0.0"
>
> So after this fix structure rte_eth_dev_data[] will keep all data one after
> the other instead of overwriting:
> (gdb) print rte_eth_dev_data[0].name
> $52 = "3:0.1"
> (gdb) print rte_eth_dev_data[1].name
> $53 = "3:0.0"
> (gdb) print rte_eth_dev_data[2].name
> $54 = "eth_pcap0"
> (gdb) print rte_eth_dev_data[3].name
> $55 = "eth_pcap1"
> and so on will be append in the next indexes
>
> If secondary process will be turned off then also will be deleted from array:
> (gdb) print rte_eth_dev_data[0].name
> $52 = "3:0.1"
> (gdb) print rte_eth_dev_data[1].name
> $53 = "3:0.0"
> (gdb) print rte_eth_dev_data[2].name
> $54 = ""
> (gdb) print rte_eth_dev_data[3].name
> $55 = ""
> this also allows re-use index 2 and 3 for next another process
> -------------------------
>
> Breaking ABI:
> Changes in the library librte_ether causes extending existing structure
> rte_eth_dev_data with a new field lock. The reason is that this structure
> is sharing between all the processes so it should be protected against
> attempting to write from two different processes.
>
> Tomasz Kulasek sent announce ABI change in librte_ether on 21 July 2016.
> I would like to join to this breaking ABI, if it is possible.
>
> v2:
> * fix syntax error in version script
> v3:
> * changed scope of function
> * improved description
> v4:
> * fix syntax error in version script
> v5:
> * fix header file
>
> Marcin Kerlin (2):
>    librte_ether: add protection against overwrite device data
>    app/testpmd: improve handling of multiprocess
>
>   app/test-pmd/testpmd.c                 | 37 +++++++++++++-
>   app/test-pmd/testpmd.h                 |  1 +
>   lib/librte_ether/rte_ethdev.c          | 90 +++++++++++++++++++++++++++++++---
>   lib/librte_ether/rte_ethdev.h          | 12 +++++
>   lib/librte_ether/rte_ether_version.map |  6 +++
>   5 files changed, 136 insertions(+), 10 deletions(-)
>

NACK series for 16.11

The patch would break the use case where primary and secondary share 
same PCI device.

Overall, I think Thomas has already mentioned it, we need further 
discussion on the use cases
and scope of DPDK multi-process.
This could be a good topic for the upcoming DPDK Userspace event.

Sergio