From: David Ahern <dsahern@gmail.com>
To: Saeed Mahameed <saeedm@mellanox.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: max channels for mlx5
Date: Sun, 3 May 2020 18:41:40 -0600 [thread overview]
Message-ID: <198081c2-cb0d-e1d5-901c-446b63c36706@gmail.com> (raw)
Hi Saeed:
When I saw this commit last year:
commit 57c7fce14b1ad512a42abe33cb721a2ea3520d4b
Author: Fan Li <fanl@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
next reply other threads:[~2020-05-04 0:41 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-04 0:41 David Ahern [this message]
2020-05-04 21:46 ` max channels for mlx5 Saeed Mahameed
2020-05-04 23:04 ` David Ahern
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