Re: [PATCH v9 2/8] mm/huge_memory: add two new (not yet used) functions for folio_split()

Zi Yan
2025-03-05T21:10:31Z

On 5 Mar 2025, at 16:03, Hugh Dickins wrote:

> On Tue, 4 Mar 2025, Zi Yan wrote:
>> On 4 Mar 2025, at 6:49, Hugh Dickins wrote:
>>>
>>> I'd been unable to complete even a single iteration of my "kernel builds
>>> on huge tmpfs while swapping to SSD" testing during this current 6.14-rc
>>> mm.git cycle (6.14-rc itself fine) - until the last week, when some
>>> important fixes have come in, so I'm no longer getting I/O errors from
>>> ext4-on-loop0-on-huge-tmpfs, and "Huh VM_FAULT_OOM leaked" warnings: good.
>>
>> This error should be related to the other patch I sent out on using
>> xas_try_split() in shmem_large_entry_split(). Great to have you confirm
>> it fixed some of the bugs.
>>
>>>
>>> But I still can't get beyond a few iterations, a few minutes: there's
>>> some corruption of user data, which usually manifests as a kernel build
>>> failing because fixdep couldn't find some truncated-on-the-left pathname.
>>
>> It is likely that this patch might fix it (partially):
>> https://lore.kernel.org/linux-mm/56EBE3B6-99EA-470E-B2B3-92C9C13032DF@nvidia.com/.
>> Andrew has picked it yesterday.
>
> No, that's a fix to a truncation issue which I had not hit:
> I did try adding that patch, but it has not helped in my case.

Got it.

>
> Beyond checking that, I didn't have time yesterday to investigate
> further, but I'll try again today (still using last weekend's mm.git).

I am trying to replicate your runs locally. Can you clarify your steps
of “kernel builds on huge tmpfs while swapping to SSD”? Do you impose
a memory limit so that anonymous memory is swapped to SSD or make tmpfs
swap to SSD?

Thanks.

Best Regards,
Yan, Zi