Re: [PATCH net-next v9 2/5] net: spacemit: Add K1 Ethernet MAC

On 9/6/25 07:59, Jakub Kicinski wrote:

On Sat, 6 Sep 2025 00:35:37 +0800 Vivian Wang wrote:

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On a closer look, these counters in ndev->stats seems to be redundant
with the hardware-tracked statistics, so maybe I should just not bother
with updating ndev->stats. Does that make sense?  

For rx/tx packets/bytes I think that makes sense.
But what about rx/tx drops?  

Right... but tstats doesn't have *_dropped. It seems that tx_dropped and
rx_dropped are considered "slow path" for real devices. It makes sense
to me that those should be very rare.

Pretty sure Simon meant the per-cpu netdev stats in general.
There are three types of them, if you need drops I think you
probably want dstats. Take a look.

According to this comment in net/core/dev.c dev_get_stats():

    /*
     * IPv{4,6} and udp tunnels share common stat helpers and use
     * different stat type (NETDEV_PCPU_STAT_TSTATS vs
     * NETDEV_PCPU_STAT_DSTATS). Ensure the accounting is consistent.
     */

"dstats" is meant for tunnels. This doesn't look like the right thing to
use, and no other pcpu_stat_type gives me tx_dropped. Do you think I
should use dstats anyway?

(And yes the only software-tracked one should be tx_dropped. Since we
pre-allocate the RX buffers, there is no opportunity to drop on RX in
software.)