[Pkg-ofed-devel] Setting mtu to 4k does not work

Simon Kainz simon.kainz at tugraz.at
Wed Oct 14 12:18:22 UTC 2009

We are trying to set the MTU to 4k on this card:

82:00.0 InfiniBand: Mellanox Technologies MT25418 [ConnectX IB DDR, PCIe
2.0 2.5GT/s] (rev a0)


mlx4_core with debug_level=1 set_4k_mtu=1

only show this in dmesg, nothing about not set mtu's:

mlx4_core 0000:82:00.0: Local CA ACK delay: 15, max MTU: 4096, port
width cap: 3

ibv_devinfo also tells me the card is capable ob 4k mtu's.

node2:~# ibv_devinfo
hca_id: mlx4_0
        fw_ver:                         2.6.900
        node_guid:                      0003:ba00:0100:7214
        sys_image_guid:                 0003:ba00:0100:7217
        vendor_id:                      0x02c9
        vendor_part_id:                 25418
        hw_ver:                         0xA0
        board_id:                       MT_04C0110002
        phys_port_cnt:                  2
                port:   1
                        state:                  PORT_ACTIVE (4)
                        max_mtu:                4096 (5)
                        active_mtu:             2048 (4)
                        sm_lid:                 1
                        port_lid:               1
                        port_lmc:               0x00

                port:   2
                        state:                  PORT_DOWN (1)
                        max_mtu:                4096 (5)
                        active_mtu:             4096 (5)
                        sm_lid:                 0
                        port_lid:               0
                        port_lmc:               0x00

Any idea on how to resolve this issue? Is it even worth it?


DI Simon Kainz
Graz, University of Technology
Department Computing
Phone: ++43 (0) 316 / 873 6885

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