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Date: Sun, 20 Sep 2026 16:54:24 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Kiryl Shutsemau <kirill@shutemov.name>
Cc: "David Hildenbrand (Arm)" <david@kernel.org>, "Lorenzo Stoakes (ARM)"
 <ljs@kernel.org>, Mike Rapoport <rppt@kernel.org>, Baolin Wang
 <baolin.wang@linux.alibaba.com>, "Kiryl Shutsemau (Meta)" <kas@kernel.org>,
 linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
 linux-kernel@vger.kernel.org, Muhammad Usama Anjum <usama.anjum@arm.com>,
 Usama Arif <usama.arif@linux.dev>, "Nico Pache (Red Hat)"
 <nico.pache@linux.dev>, Zi Yan <ziy@nvidia.com>, Barry Song
 <baohua@kernel.org>, Dev Jain <dev.jain@arm.com>, Hugh Dickins
 <hughd@google.com>, Lance Yang <lance.yang@linux.dev>, "Liam R. Howlett"
 <liam@infradead.org>, Michal Hocko <mhocko@suse.com>, Ryan Roberts
 <ryan.roberts@arm.com>, Shuah Khan <shuah@kernel.org>, Suren Baghdasaryan
 <surenb@google.com>, "Vlastimil Babka (SUSE)" <vbabka@kernel.org>,
 Alexander Gordeev <agordeev@linux.ibm.com>, Jason Gunthorpe <jgg@ziepe.ca>,
 Leon Romanovsky <leon@kernel.org>, kernel-team@meta.com
Subject: Re: [PATCH v6 00/19] selftests/mm: improve khugepaged coverage
Message-Id: <20260920165424.adbd45ccfc6162ffb0e4b424@linux-foundation.org>
In-Reply-To: <20260919002451.496763-1-kirill@shutemov.name>
References: <20260919002451.496763-1-kirill@shutemov.name>
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On Sat, 19 Sep 2026 01:24:30 +0100 Kiryl Shutsemau <kirill@shutemov.name> wrote:

> From: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
> 
> khugepaged collapses to mTHP orders since 7.2, and 7.3 added three
> selftest cases for it: the generic collapse cases run at one order named
> by -c, with the result detected by counting folios of that order.
> 
> That leaves the collapse path largely untested.  The suite does not run
> where a PMD is 512M.  A folio count cannot say where a collapse landed.
> Fixed sleeps cannot tell "not collapsed" from "not scanned yet".  And
> nothing exercises collapse under contention.
> 
> Close those gaps in order:
> 

Thanks, I've added this to mm-new.

I'd previous added v5 but it never really got testing exposure due to a
messy interaction with other changes which I didn't get onto fixing.