Re: [PATCH 00/53] selftests/mm: make MM selftests more CI friendly

[Ryan Roberts <ryan.roberts@arm.com>]

On 20/04/2026 10:19, Mike Rapoport wrote:
> Hi Ryan,
> 
> On Mon, Apr 20, 2026 at 09:37:03AM +0100, Ryan Roberts wrote:
>> On 06/04/2026 15:16, Mike Rapoport wrote:
>>> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
>>>
>>> Hi,
>>>
>>> There's a lot of dancing around HugeTLB settings in run_vmtests.sh.
>>> Some test need just a few default huge pages, some require at least 256 MB, and
>>> some just skip lots of tests if huge pages of all supported sizes are not
>>> available.
>>>
>>> The goal of this set is to make tests deal with HugeTLB setup and teardown.
>>
>> Hi Mike,
>>
>> I haven't had a chance to review this series properly, but the intent certainly
>> seems extremely valuable!
>>
>> I thought I'd share some configuration magic that I always use when running on
>> arm64. Appologies if I'm teaching you to suck eggs...
>>
>> arm64 supports multiple hugetlb sizes and (at least in the past) the magic in
>> run_vmtests.sh only reserves for the default size. As a consequence, whenever I
>> run these tests on arm64, I always boot with:
>>
>> hugepagesz=1G hugepages=0:2,1:2
>> hugepagesz=32M hugepages=0:2,1:2
>> default_hugepagesz=2M hugepages=0:64,1:64
>> hugepagesz=64K hugepages=0:2,1:2
>>
>> Which reserves 2 pages of each supported non-default size in each of 2 NUMA
>> nodes, and 64 of the default size in each NUMA node. (This would need adjusting
>> if using a different base page size).
>>
>> My recollection is that this effectively overrides what the script was doing and
>> is sufficient to make all hugetlb tests run for all hugepage sizes.
> 
> My goal is to let the tests themself set up the right hugetlb configuration
> without forcing it neither in command line nor in the wrapper scripts.
> 
> On x86 I can run all the tests in a virtio-ng VM with two nodes and no
> kernel command line overrides. I suppose that should work on arm64 too.
> 
> There are some additional settings that such a VM would need to avoid
> skipping tests that presume swap or a real filesystem, but that's more of
> virtio-ng limitation.
> 
>> If it's possible to get this non-default hugepage size reservation logic into
>> the tests themselves, this will make the mm selftests much easier to run on
>> arm64 with full coverage.
> 
> That's what the second half of series do. E.g for cow tests:
> 
> https://lore.kernel.org/linux-mm/ee6bbac9-b375-4413-a771-6d32c7afda67@arm.com/T/#m62f23b835061449bc6249afacf993bb32ea11234

Ahh, excellent; you're already considering the non-default sizes. I'll get back
in my box :)

>  
>> Another observation is that "secretmem.enable" is currently needed on the
>> cmdline to enable secretmem so that the associated tests run. Not sure what can
>> be done to make that simpler?
> 
> Looks like you're testing really old kernels :)
> The secretmem default changed to "enabled" from 6.5 ;-)

Good to know; I created my scripts/environment pre-6.5, so that's just
historical baggage on my part, I guess.

>  
>> And there are tests that depend on having more than 1 NUMA node; I always run
>> under QEMU with 2 emulated NUMA nodes. I guess that's really just a property of
>> the HW, so nothing to be done from the test harness.
> 
> Right, test harness can't do much about it. It's either run in a virtual
> machines with 2 (or more) nodes or enable NUMA emulation in the kernel
> configuration and the kernel command line.

ACK

Thanks again for this improvement!

> 
>> Thanks,
>> Ryan
>