Re: [PATCH v5 02/19] selftests/mm: skip collapse_compound_extreme() where the PMD is too large

[Baolin Wang]

On 9/8/26 8:50 PM, Kiryl Shutsemau wrote:
> From: "Kiryl Shutsemau (Meta)" <kas@xxxxxxxxxx>
>
> collapse_compound_extreme() builds a PTE table full of distinct PTE-mapped
> compound pages by cycling hpage_pmd_nr fault-time THPs through mremap.  It
> therefore needs hpage_pmd_nr PMD-order allocations in a row.  That is fine
> at a 2M PMD (4K base pages) or a 32M one (16K).  A 512M PMD -- arm64 with
> 64K base pages -- makes each of those an order-13 allocation, which the
> allocator cannot reliably hand out even once, let alone 8192 times.
>
> The failure is not a quiet one: the case calls ksft_exit_fail_msg(), so the
> whole binary stops and every case after it is lost.
>
> Skip the case where the PMD is larger than 32M.  The MADV_COLLAPSE cases
> still cover PMD-order collapse on those configurations, and 4K and 16K
> PMDs are unaffected.
>
> Assisted-by: LLM
> Acked-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
> Tested-by: Muhammad Usama Anjum <usama.anjum@xxxxxxx>
> Signed-off-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>
> ---

LGTM.
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>