Re: [PATCH] net/mlx5: enable PCI related counters

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri,  9 Feb 2024 20:41:42 +0000
Wathsala Vithanage <wathsala.vithanage@arm.com> wrote:

> Versions of Mellanox NICs starting from CX5 have device counters
> related to PCI. These counters are helpful in debugging IO
> bottlenecks. For instance, the outbound_pci_stalled_rd and
> outbound_pci_stalled_wr counters can help with identifying NIC
> stalls due to insufficient PCI credits, which otherwise would
> have required a PCI analyzer or a sophisticated PCI root port
> with a PMU.
> Currently none of these are available in the MLX5 PMD even
> though ethtool is capable of reading some of them.
> Since PMD uses the same ioctl used by ethtool (SIOCETHTOOL) and
> reads via the kernel driver it is possible to add support with
> ease.
> There is one more PCI related counter and a device counter that
> aren't implemented in the Linux driver at the moment. These two
> are named outbound_pci_buffer_overflow and dev_out_of_buffer
> respectively. As per Nvidia's documentation these two counters
> can tell the number of packets dropped due to pci buffer
> overflow and the number of times the device owned queue had not
> enough buffers allocated.
> 
> Signed-off-by: Wathsala Vithanage <wathsala.vithanage@arm.com>
> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>

Would it be possible to do this at PCI bus layer so all PCI devices have
that feature?