Hi Saeed:
When I saw this commit last year:
commit 57c7fce14b1ad512a42abe33cb721a2ea3520d4b
Author: Fan Li <f...@mellanox.com>
Date: Mon Dec 16 14:46:15 2019 +0200
net/mlx5: Increase the max number of channels to 128
I was expecting to be able to increase the number of channels on larger
systems (e.g., 96 cpus), but that is not working as I expected.
This is on net-next as of today:
60bcbc41ffb3 ("Merge branch 'net-smc-add-and-delete-link-processing'")
$ sudo ethtool -L eth0 combined 95
Cannot set device channel parameters: Invalid argument
As it stands the maximum is 63 (or is it 64 and cpus 0-63?):
$ sudo ethtool -l eth0
Channel parameters for eth0:
Pre-set maximums:
RX: 0
TX: 0
Other: 0
Combined: 63
Current hardware settings:
RX: 0
TX: 0
Other: 0
Combined: 63
A side effect of this limit is XDP_REDIRECT drops packets if a vhost
thread gets scheduled on cpus 64 and up since the tx queue is based on
processor id:
int mlx5e_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames,
u32 flags)
{
...
sq_num = smp_processor_id();
if (unlikely(sq_num >= priv->channels.num))
return -ENXIO;
So in my example if the redirect happens on cpus 64-95, which is 1/3 of
my hardware threads, the packet is just dropped.
Am I missing something about how to use the expanded maximum?
David
