Re: [PATCH] Revert "perf/aux: Allocate non-contiguous AUX pages by default"

[sashiko-bot@kernel.org]

> This reverts commit 18049c8cff9cc89daadc4df6975f7d9069638926.
> 
> The original commit claimed that contiguous AUX pages unnecessarily
> exacerbate fragmentation for SPE, TRBE and ETR. This is not generally
> valid: larger allocations can keep pages with the same lifetime
> together, while order-0 allocations can scatter them across large
> blocks and prevent free pages from coalescing [1]. The follow-up
> discussion [2] has not established how forcing order-0 allocations
> addresses the reported problem.
> 
> TRBE and SPE write to virtually addressed buffers. The TRBE L1 TLB
> has one entry on Neoverse V2 [3] and two on Neoverse V3 [4]. Small
> mappings increase translation pressure, and TTW stalls can contribute
> to FIFO overflow and trace loss on TRBE.
> 
> [ ... ]
> [3] https://documentation-service.arm.com/static/633fe1ec4c59b30b517730b8#page=52
> [4] https://documentation-service.arm.com/static/67361bd2c7fc0d1f211da382#page=54
> [5] https://lore.kernel.org/linux-mm/20260715120813.3609949-1-jiangwen6@xiaomi.com/
> 
> Signed-off-by: Leo Yan <leo.yan@arm.com>

Sashiko has reviewed this patch and found no issues.

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