Netmap on Linux nm_open() fail when receive ring size is set to 4096

[Vincenzo Maffione]

Hi,
  You need to increase the value of some netmap module parameter. At least
ring_size, maybe also buf_num. Then restart your netmap applications.

Keep in mind that performance could worsen with more slots, because of
increased cache thrashing.

Cheers,
  Vincenzo


On Wed, Mar 28, 2018, 3:50 PM Ming Fu <Ming.Fu at esentire.com> wrote:

> Hi,
>
> I was trying netmap on a Linux box with 128G of ram (64G per numa node).
> If I set ixgbe interface to 4096 ring size, the nm_open will fail with
> error "Cannot allocate memory". What can I tweak to make the card use
> larger ring size? The following test was run after fresh reboot.
>
> $ ethtool -g enp5s0f0
> Ring parameters for enp5s0f0:
> Pre-set maximums:
> RX:                        4096
> RX Mini:               0
> RX Jumbo:           0
> TX:                        4096
> Current hardware settings:
> RX:                        512
> RX Mini:               0
> RX Jumbo:           0
> TX:                        512
>
> $ ethtool -G enp5s0f0 rx 1024
> $ ./nmtest -i enp5s0f0
> ^C
> $ ethtool -G enp5s0f0 rx 2048
> $ nmtest -i enp5s0f0
> ^C
> $ ethtool -G enp5s0f0 rx 4096
> $ nmtest -i enp5s0f0
> 816.039684 nm_open [945] NIOCREGIF failed: Cannot allocate memory
> netmap:enp5s0f0
> fail to nm_open(netmap:enp5s0f0 ... ): Cannot allocate memory
>
> Thanks,
> Ming
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