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

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Message-ID: <20200410145804.fczyvec4pngpep6t@box>
Date:   Fri, 10 Apr 2020 17:58:04 +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 Fri, Apr 10, 2020 at 10:36:58AM -0400, Zi Yan wrote:
> 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’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?
> 
> First of all, the failure above was from a bare metal and was the only
> failure I saw, whereas I saw more failures in my VM. The test program
> was not messed up in either environment.

Hm. In the quote you are saying "BTW, I am running in a VM".

> 
> For VM failures I mentioned before, I used scp to copy the source code
> into the VM. My VM has its port 22 forwarded to host’s port 11022. “-net
> user,hostfwd=tcp::11022-:22”. I also copied a binary 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 slash
> > was converted to single. As result check_huge() and check_swap() gave the
> > false-negative result all the time.
> 
> It was not my case, since CHECK_HUGE_FMT and CHECK_SWAP_FMT from my
> khugepaged.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.

My config is attached.


-- 
 Kirill A. Shutemov

View attachment ".config" of type "text/plain" (131146 bytes)