Re: [PATCH net-next] udp: add drop count for packets in udp_prod_queue

Mahdi Faramarzpour wrote:

On Tue, Jan 6, 2026 at 10:52 PM Willem de Bruijn
[off-list ref] wrote:

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Mahdi Faramarzpour wrote:

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On Tue, Jan 6, 2026 at 5:24 AM Jakub Kicinski [off-list ref] wrote:

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On Mon,  5 Jan 2026 15:17:32 +0330 Mahdi Faramarzpour wrote:

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This commit adds SNMP drop count increment for the packets in
per NUMA queues which were introduced in commit b650bf0977d3
("udp: remove busylock and add per NUMA queues").

Can you give some rationale why the existing counters are insufficient
and why you chose to change then number of counters you suggest
between revisions of your patch?

The difference between revisions is due to me realizing that the only error the
udp_rmem_schedule returns is ENOBUFS, which is mapped to UDP_MIB_MEMERRORS
(refer to function __udp_queue_rcv_skb), and thus UDP_MIB_RCVBUFERRORS
need not increase.

I see. Please make such a note in the revision changelog. See also

https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html#changes-requested

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This code adds some cost to the hot path. The blamed commit added
drop counters, most likely weighing the value of counters against
their cost. I don't immediately see reason to revisit that.

AFAIU the drop_counter is per socket, while the counters added in this
patch correspond
to /proc/net/{snmp,snmp6} pseudofiles. This patch implements the todo
comment added in
the blamed commit.

Ah indeed.

The entire logic can be inside the unlikely(to_drop) branch right?
No need to initialize the counters in the hot path, or do the
skb->protocol earlier?

The previous busylock approach could also drop packets at this stage
(goto uncharge_drop), and the skb is also dropped if exceeding rcvbuf.
Neither of those conditions update SNMP stats. I'd like to understand
what makes this case different.

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You must not submit more than one version of a patch within a 24h
period.

Hi Jakub and sorry for the noise, didn't know that. Is there any way to check
my patch against all patchwork checks ,specially the AI-reviewer
before submitting it?

See https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html

thanks.