Re: [PATCH 2/2] perf: arm_spe: Prefer large AUX mappings

[Will Deacon]

On Mon, Aug 10, 2026 at 03:44:42PM +0100, Leo Yan wrote:
> Commit 18049c8cff9c ("perf/aux: Allocate non-contiguous AUX pages by
> default") made the AUX allocator use order-0 pages by default unless a
> PMU explicitly asks for contiguous allocations.

But that commit specifically calls out SPE as benefitting from
non-contiguous pages:

  "For instance, ARM SPE and TRBE operate with virtual pages, and
   Coresight ETR allocates a separate buffer. For these PMUs,
   allocating contiguous AUX pages unnecessarily exacerbates memory
   fragmentation. This fragmentation can prevent their use on
   long-running devices."

so why doesn't passing PERF_PMU_CAP_AUX_PREFER_LARGE reintroduce the
problems that 18049c8cff9c was trying to solve?

Will