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From:   Zi Yan <ziy@nvidia.com>
To:     "Kirill A. Shutemov" <kirill@shutemov.name>
CC:     <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        "Yang Shi" <yang.shi@linux.alibaba.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCHv2 1/8] khugepaged: Add self test
Date:   Fri, 10 Apr 2020 10:36:58 -0400
Message-ID: <DF6A7119-D6D6-4679-A4B6-9A7570984D97@nvidia.com>
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On 10 Apr 2020, at 7:47, Kirill A. Shutemov wrote:

> External email: Use caution opening links or attachments
>
>
> On Mon, Apr 06, 2020 at 10:59:52AM -0400, Zi Yan wrote:
>> I ran this test with all patches from this series applied to Linus=E2=80=
=99s tree, but still see several failures. Is it expected?
>> The config file is attached. Let me know if I miss anything. BTW, I am=
 running in a VM.
>>
>> Thanks.
>>
>> The output:
>>
>> =E2=9E=9C  ~ sudo ./khugepaged
>> Save THP and khugepaged settings... OK
>> Adjust settings... OK
>> Allocate huge page on fault... OK
>> Split huge PMD on MADV_DONTNEED... OK
>> Collapse fully populated PTE table.... Fail
>
> I was able to reproduce the issue. And it's fun failure mode.
>
> How did you get the test case inside the VM? Copy-paste source using 'c=
at'
> or something similar inside the VM?

First of all, the failure above was from a bare metal and was the only fa=
ilure I saw, whereas I saw more failures in my VM. The test program was n=
ot messed up in either environment.

For VM failures I mentioned before, I used scp to copy the source code in=
to the VM. My VM has its port 22 forwarded to host=E2=80=99s port 11022. =
=E2=80=9C-net user,hostfwd=3Dtcp::11022-:22=E2=80=9D. I also copied a bin=
ary into my VM and saw the same failures.

I kinda think the failures are not related to your patches but something =
else.

>
> It screwed up CHECK_HUGE_FMT and CHECK_SWAP_FMT for me. Double back sla=
sh
> was converted to single. As result check_huge() and check_swap() gave t=
he
> false-negative result all the time.

It was not my case, since CHECK_HUGE_FMT and CHECK_SWAP_FMT from my khuge=
paged.c match your patch code.

>
> Could you check that the source of the test-case is not mangled and
> re-test if it is.

I can confirm that the test-case is not mangled. I think it must be my VM=
 setup or kernel configuration.

Do you mind sharing your .config file with me and which kernel commit you=
 apply the patches on top of in your setup? I can look into it and check =
what the problem is.

Thanks.


--
Best Regards,
Yan Zi

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