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

[Ming Fu]

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