linux-kernel - Re: [PATCHv2 1/8] khugepaged: Add self test

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Message-ID: <20200410114739.b2ndracbyhsdmanv@box>
Date:   Fri, 10 Apr 2020 14:47:39 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Zi Yan <ziy@...dia.com>
Cc:     akpm@...ux-foundation.org, Andrea Arcangeli <aarcange@...hat.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCHv2 1/8] khugepaged: Add self test

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’s 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:
> 
> ➜  ~ 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 'cat'
or something similar inside the VM?

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

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

-- 
 Kirill A. Shutemov