Re: [PATCH v5 12/19] selftests/mm: parameterize the mixed-source collapse case by source order

[Kiryl Shutsemau <kirill@shutemov.name>]

On Thu, Sep 10, 2026 at 01:09:00PM +0800, Baolin Wang wrote:
> 
> 
> On 9/8/26 8:50 PM, Kiryl Shutsemau wrote:
> > From: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
> > 
> > collapse_order_mixed_sources() faults its region as order-2 folios and
> > collapses them to the -c target.  Order 2 is below the contpte size on
> > every arm64 page size, so nothing in this suite collapses a contpte-mapped
> > source on purpose.
> > 
> > Let -s name the source order alongside -c.  The case then faults at that
> > order, keeping order 2 when -s is absent, and the source order has to be a
> > supported mTHP order below the target.  The other mTHP cases are
> > unaffected: mthp_push_target_order() enables only the target order.
> > 
> > "-s 5 -c 7" on arm64/64K then collapses contpte-mapped sources into a
> > larger mTHP.
> 
> Make sense. But we should validate invalid parameter combinations for '-s'
> and '-c'. For example, when I set the following unreasonable parameters,
> some test cases fail, so such invalid configurations should be rejected.

Patch 14 adds that check; with the whole series applied,
"-s 7 -c 6 mthp_khugepaged:anon" stops before running anything:

  1..0 # SKIP -c 6 needs a source order below it, -s says 7

So this is a minor bisectability issue: the check should have come with
this patch rather than two later.  I will move it here if the series gets
respun.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov