Re: [PATCH RFC v2] mm: memory-tiering: Fix PGPROMOTE_CANDIDATE accounting

[Huang, Ying]

"Zhijian Li (Fujitsu)" <lizhijian@xxxxxxxxxxx> writes:

> Hi,
>
>
> On 25/06/2025 10:13, Li Zhijian wrote:
>> V2:
>> Fix compiling error # Reported by LKP
>> 
>> As Ying suggested, we need to assess whether this change causes regression.
>> However, considering the stringent conditions this patch involves,
>> properly evaluating it may be challenging, as the outcomes depend on your
>> perspective. Much like in a zero-sum game, if someone benefits, another
>> might lose.
>> 
>> If there are subsequent results, I will update them here.
>
> I ran memhog + pmbench to evaluate the impact of the patch(3 runs [1] for each kernel).
>
> The results show an approximate 4% performance increase in pmbench after applying this patch.
>
> Average     pmbench-access            max-promotion-rate
> Before:     7956805 pages/sec                168301 pages/sec
> After:      8313666 pages/sec (+4.4%)        207149 pages/sec

It's hard for me to understand why performance increases because of
higher promotion rate, while the expected behavior is more promotion
rate limiting.

> The detailed logs are available at [2].
>
> [1] https://github.com/zhijianli88/misc/blob/main/20250627/promotion-evaluation/reproduce.sh
> [2] https://github.com/zhijianli88/misc/tree/main/20250627/promotion-evaluation

[snip]

---
Best Regards,
Huang, Ying