Re: git: 0ec13430c583 - main - sys/netinet6: Fix ABI breakage introduced with RFC 7217 support

On 9/23/25 18:16, Zhenlei Huang wrote:
> 
> 
>> On Sep 23, 2025, at 11:48 PM, Guido Falsi <madpilot@FreeBSD.org> wrote:
>>
>> On 9/23/25 17:27, Jonathan T. Looney wrote:
>>> On Mon, Sep 22, 2025 at 11:44 AM Guido Falsi <madpilot@freebsd.org <mailto:madpilot@freebsd.org>> wrote:
>>>     On 9/22/25 17:37, Jonathan T. Looney wrote:
>>>      > This seems like it is probably a low-frequency event. If so, why
>>>     is a
>>>      > counter a better choice for this than an atomic?
>>>      >
>>>     I used counters because they were already being used in the netinet6
>>>     code, and are a good match for the use.
>>> What makes them a good match for the use? Counters are generally best for write-often, read-rarely (by comparison) things, like statistics, where we want to avoid contention in a often-used critical path. For low-frequency events, the expense of keeping the counters (memory usage multiplied by the number of cores; more difficult debugging; etc.) may outweigh the benefits.
>>
>> Maybe I explained myself poorly, I meant to say the structure already uses counters and they work.
> 
> Jonathan is not talking about the correctness but he hints it is overkill to use a counter(9) for a rarely updated struct member.
> 
>>
>> It did not occur to me to use something different, but I see no problem using a different tool, as long as it works and does not make the logic more complex.
> 
> An atomic(9) is sufficient, so you can eliminate alloc / free and the code is shorter :)

Thanks for the clarification.

I'll take a look then, if the code can be improved I'm all in favour of 
that.

-- 
Guido Falsi <madpilot@FreeBSD.org>