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

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Message-ID: <C66E1309-2069-495B-BACD-7F3282C6EC7D@nvidia.com>
Date:   Wed, 8 Apr 2020 11:53:52 -0400
From:   Zi Yan <ziy@...dia.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
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 8 Apr 2020, at 10:21, Kirill A. Shutemov wrote:

> External email: Use caution opening links or attachments
>
>
> On Mon, Apr 06, 2020 at 02:50:32PM -0400, Zi Yan wrote:
>>       khugepaged-58    [001] ....  9913.990380: mm_khugepaged_scan_pmd: mm=00000000283d31fc, scan_pfn=0x2ae4bd, writable=0, referenced=512, none_or_zero=0, status=no_writable_page, unmapped=0
>
> Looks like all failures due to lack of writable ptes. That's very strange
> because we write to the page on fill.
>
> You've mentioned that you run it in VM. I wounder if it can be a
> virtualizaiton artefact. I run tests under KVM and they are fine. What is
> your virtualization setup?

My qemu cmd: “qemu-system-x86_64 -kernel ~/repos/linux/arch/x86/boot/bzImage -hda ~/qemu-image/vm.qcow2 -append "root=/dev/sda1 rw console=ttyS0" -pidfile vm.pid -net user,hostfwd=tcp::11022-:22 -net nic -numa node,nodeid=0 -numa node,nodeid=1 -m 20g -smp 8 -cpu host -enable-kvm -nographic”

QEMU version is 4.2.0 (Debian 1:4.2-3)

The patches are applied on top of commit a10c9c710f9ecea87b9f4bbb837467893b4bef01 from Linus’s tree.


In addition, I tested it again on a bare metal, then all tests passed except “Collapse with max_ptes_swap pages swapped out”, which failed most of time but succeeded occasionally.

When it fails, the tracing info is (seems like the same PTE not writable issue):

# sudo ./trace.sh
Save THP and khugepaged settings... OK
Adjust settings... OK
Swapout 64 of 512 pages... OK
Collapse with max_ptes_swap pages swapped out.... Fail
Restore THP and khugepaged settings... OK
# tracer: nop
#
# entries-in-buffer/entries-written: 42/42   #P:48
#
#                              _-----=> irqs-off
#                             / _----=> need-resched
#                            | / _---=> hardirq/softirq
#                            || / _--=> preempt-depth
#                            ||| /     delay
#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
#              | |       |   ||||       |         |
      khugepaged-265   [002] ...1  1007.308366: mm_collapse_huge_page_swapin: mm=000000007c6cc479, swapped_in=64, referenced=448, ret=1
      khugepaged-265   [002] ...2  1007.308403: mm_collapse_huge_page_isolate: scan_pfn=0x1faa6ee, none_or_zero=0, referenced=60, writable=0, status=not_suitable_page_count
      khugepaged-265   [002] ...1  1007.308404: mm_collapse_huge_page: mm=000000007c6cc479, isolated=0, status=failed
      khugepaged-265   [002] ...1  1007.308405: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1fafa45, writable=1, referenced=448, none_or_zero=0, status=succeeded, unmapped=64
      khugepaged-265   [002] ...1  1007.328249: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.344263: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.360263: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.376241: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.392237: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.408284: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.424302: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.440284: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.456285: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.472280: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.488282: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.504264: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.520293: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.536282: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.552278: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.568302: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.584290: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.600300: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.616292: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.632290: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.648304: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.664305: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.680289: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.696294: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.712294: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.728309: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.744291: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.760288: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.776312: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.792288: mm_khugepaged_scan_pmd: mm=000000007c6cc479, scan_pfn=0x1faa6ee, writable=0, referenced=60, none_or_zero=0, status=not_suitable_page_count, unmapped=0
      khugepaged-265   [002] ...1  1007.811482: mm_khugepaged_scan_pmd: mm=000000006aaca29d, scan_pfn=0xffffffffffffffff, writable=0, referenced=0, none_or_zero=0, status=pmd_null, unmapped=0
      khugepaged-265   [002] ...1  1007.811482: mm_khugepaged_scan_pmd: mm=000000006aaca29d, scan_pfn=0xffffffffffffffff, writable=0, referenced=0, none_or_zero=0, status=pmd_null, unmapped=0
      khugepaged-265   [002] ...1  1007.811483: mm_khugepaged_scan_pmd: mm=000000006aaca29d, scan_pfn=0xffffffffffffffff, writable=0, referenced=0, none_or_zero=0, status=pmd_null, unmapped=0
      khugepaged-265   [002] ...1  1007.811483: mm_khugepaged_scan_pmd: mm=000000006aaca29d, scan_pfn=0xffffffffffffffff, writable=0, referenced=0, none_or_zero=0, status=pmd_null, unmapped=0
      khugepaged-265   [002] ...1  1007.811483: mm_khugepaged_scan_pmd: mm=000000006aaca29d, scan_pfn=0xffffffffffffffff, writable=0, referenced=0, none_or_zero=0, status=pmd_null, unmapped=0
      khugepaged-265   [002] ...1  1007.811484: mm_khugepaged_scan_pmd: mm=000000006aaca29d, scan_pfn=0xffffffffffffffff, writable=0, referenced=0, none_or_zero=0, status=pmd_null, unmapped=0
      khugepaged-265   [002] ...1  1007.811502: mm_khugepaged_scan_pmd: mm=000000005268d9a7, scan_pfn=0xffffffffffffffff, writable=0, referenced=0, none_or_zero=0, status=pmd_null, unmapped=0
      khugepaged-265   [002] ...1  1007.811502: mm_khugepaged_scan_pmd: mm=000000005268d9a7, scan_pfn=0xffffffffffffffff, writable=0, referenced=0, none_or_zero=0, status=pmd_null, unmapped=0


—
Best Regards,
Yan Zi

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