Date:   Wed, 21 Nov 2018 22:29:39 +0100
From:   Paweł Staszewski <pstaszewski@...are.pl>
To:     Toke Høiland-Jørgensen <toke@...e.dk>,
        David Ahern <dsahern@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc:     Jesper Dangaard Brouer <brouer@...hat.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jason Wang <jasowang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        David Miller <davem@...emloft.net>
Subject: Re: consistency for statistics with XDP mode


W dniu 21.11.2018 o 22:14, Toke Høiland-Jørgensen pisze:
> David Ahern <dsahern@...il.com> writes:
>
>> Paweł ran some more XDP tests yesterday and from it found a couple of
>> issues. One is a panic in the mlx5 driver unloading the bpf program
>> (mlx5e_xdp_xmit); he will send a send a separate email for that
>> problem.
> Same as this one, I guess?
>
> https://marc.info/?l=linux-netdev&m=153855905619717&w=2

Yes same as this one.

When there is no traffic (for example with xdp_fwd program loaded) or 
there is not much traffic like 1k frames per second for icmp - i can 
load/unload without crashing kernel

But when i push tests with pktgen and use more than >50k pps for udp - 
then unbinding xdp_fwd program makes kernel to panic :)



>
>> The problem I wanted to discuss here is statistics for XDP context. The
>> short of it is that we need consistency in the counters across NIC
>> drivers and virtual devices. Right now stats are specific to a driver
>> with no clear accounting for the packets and bytes handled in XDP.
>>
>> For example virtio has some stats as device private data extracted via
>> ethtool:
>> $ ethtool -S eth2 | grep xdp
>>      ...
>>       rx_queue_3_xdp_packets: 5291
>>       rx_queue_3_xdp_tx: 0
>>       rx_queue_3_xdp_redirects: 5163
>>       rx_queue_3_xdp_drops: 0
>>      ...
>>       tx_queue_3_xdp_tx: 5163
>>       tx_queue_3_xdp_tx_drops: 0
>>
>> And the standard counters appear to track bytes and packets for Rx, but
>> not Tx if the packet is forwarded in XDP.
>>
>> Similarly, mlx5 has some counters (thanks to Jesper and Toke for helping
>> out here):
>>
>> $ ethtool -S mlx5p1 | grep xdp
>>       rx_xdp_drop: 86468350180
>>       rx_xdp_redirect: 18860584
>>       rx_xdp_tx_xmit: 0
>>       rx_xdp_tx_full: 0
>>       rx_xdp_tx_err: 0
>>       rx_xdp_tx_cqe: 0
>>       tx_xdp_xmit: 0
>>       tx_xdp_full: 0
>>       tx_xdp_err: 0
>>       tx_xdp_cqes: 0
>>      ...
>>       rx3_xdp_drop: 86468350180
>>       rx3_xdp_redirect: 18860556
>>       rx3_xdp_tx_xmit: 0
>>       rx3_xdp_tx_full: 0
>>       rx3_xdp_tx_err: 0
>>       rx3_xdp_tx_cqes: 0
>>      ...
>>       tx0_xdp_xmit: 0
>>       tx0_xdp_full: 0
>>       tx0_xdp_err: 0
>>       tx0_xdp_cqes: 0
>>      ...
>>
>> And no accounting in standard stats for packets handled in XDP.
>>
>> And then if I understand Jesper's data correctly, the i40e driver does
>> not have device specific data:
>>
>> $ ethtool -S i40e1  | grep xdp
>> [NOTHING]
>>
>>
>> But rather bumps the standard counters:
>>
>> sudo ./xdp_rxq_info --dev i40e1 --action XDP_DROP
>>
>> Running XDP on dev:i40e1 (ifindex:3) action:XDP_DROP options:no_touch
>> XDP stats       CPU     pps         issue-pps
>> XDP-RX CPU      1       36,156,872  0
>> XDP-RX CPU      total   36,156,872
>>
>> RXQ stats       RXQ:CPU pps         issue-pps
>> rx_queue_index    1:1   36,156,878  0
>> rx_queue_index    1:sum 36,156,878
>>
>>
>> $ ethtool_stats.pl --dev i40e1
>>
>> Show adapter(s) (i40e1) statistics (ONLY that changed!)
>> Ethtool(i40e1   ) stat:   2711292859 (  2,711,292,859) <= port.rx_bytes /sec
>> Ethtool(i40e1   ) stat:      6274204 (      6,274,204) <=
>> port.rx_dropped /sec
>> Ethtool(i40e1   ) stat:     42363867 (     42,363,867) <=
>> port.rx_size_64 /sec
>> Ethtool(i40e1   ) stat:     42363950 (     42,363,950) <=
>> port.rx_unicast /sec
>> Ethtool(i40e1   ) stat:   2165051990 (  2,165,051,990) <= rx-1.bytes /sec
>> Ethtool(i40e1   ) stat:     36084200 (     36,084,200) <= rx-1.packets /sec
>> Ethtool(i40e1   ) stat:         5385 (          5,385) <= rx_dropped /sec
>> Ethtool(i40e1   ) stat:     36089727 (     36,089,727) <= rx_unicast /sec
>>
>>
>> We really need consistency in the counters and at a minimum, users
>> should be able to track packet and byte counters for both Rx and Tx
>> including XDP.
>>
>> It seems to me the Rx and Tx packet, byte and dropped counters returned
>> for the standard device stats (/proc/net/dev, ip -s li show, ...) should
>> include all packets managed by the driver regardless of whether they are
>> forwarded / dropped in XDP or go up the Linux stack. This also aligns
>> with mlxsw and the stats it shows which are packets handled by the hardware.
>>
>>  From there the private stats can include XDP specifics as desired --
>> like the drops and redirects but that those should be add-ons and even
>> here some consistency makes life easier for users.
>>
>> The same standards should be also be applied to virtual devices built on
>> top of the ports -- e.g,  vlans. I have an API now that allows bumping
>> stats for vlan devices.
>>
>> Keeping the basic xdp packets in the standard counters allows Paweł, for
>> example, to continue to monitor /proc/net/dev.
>>
>> Can we get agreement on this? And from there, get updates to the mlx5
>> and virtio drivers?
> I'd say it sounds reasonable to include XDP in the normal traffic
> counters, but having the detailed XDP-specific counters is quite useful
> as well... So can't we do both (for all drivers)?
>
> -Toke
>

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