[PATCH v3 0/1] mm/page_alloc: dynamic watermark boosting

[wujing <realwujing@qq.com>]

This is v3 of the auto-tuning patch, addressing feedback from Vlastimil Babka,
Andrew Morton, and Matthew Wilcox.

Major shift in v3:
Following Vlastimil's suggestion, this version abandons the direct modification
of min_free_kbytes. Instead, it leverages the existing watermark_boost
infrastructure. This approach is more idiomatic as it:
- Avoids conflicts with administrative sysctl settings.
- Only affects specific zones experiencing pressure.
- Utilizes standard kswapd logic for natural decay after reclamation.

Responses to Vlastimil Babka's feedback:
> "Were they really packet drops observed? AFAIK the receive is deferred to non-irq 
> context if those atomic allocations fail, it shouldn't mean a drop."
In our high-concurrency production environment, we observed that while the 
network stack tries to defer processing, persistent GFP_ATOMIC failures 
eventually lead to NIC-level drops due to RX buffer exhaustion.

> "As for the implementation I'd rather not be changing min_free_kbytes directly... 
> We already have watermark_boost to dynamically change watermarks"
Agreed and implemented in v3.

Changes in v3:
- Replaced min_free_kbytes modification with watermark_boost calls.
- Removed all complex decay/persistence logic from v2, relying on kswapd's 
  standard behavior.
- Maintained the 10-second debounce mechanism.
- Engaged netdev@ community as requested by Andrew Morton.

Thanks for the thoughtful reviews!

wujing (1):
  mm/page_alloc: auto-tune watermarks on atomic allocation failure

 mm/page_alloc.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

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2.39.5