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Date:   Mon, 20 Jul 2020 10:27:10 +0200
From:   osalvador@suse.de
To:     =?UTF-8?Q?HORIGUCHI_NAOYA=28=E5=A0=80=E5=8F=A3=E3=80=80=E7=9B=B4?=
         =?UTF-8?Q?=E4=B9=9F=29?= <naoya.horiguchi@nec.com>
Cc:     akpm@linux-foundation.org, Michal Hocko <MHocko@suse.com>,
        linux-mm@kvack.org, mike.kravetz@oracle.com, david@redhat.com,
        aneesh.kumar@linux.vnet.ibm.com, linux-kernel@vger.kernel.org,
        Oscar Salvador <OSalvador@suse.com>
Subject: Re: [PATCH v4 12/15] mm,hwpoison: Rework soft offline for in-use
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On 2020-07-17 08:55, HORIGUCHI NAOYA wrote:
> I ran Quan Cai's test program (https://github.com/cailca/linux-mm) on a
> small (4GB memory) VM, and weiredly found that (1) the target hugepages
> are not always dissolved and (2) dissovled hugetpages are still counted
> in "HugePages_Total:". See below:
> 
>     $ ./random 1
>     - start: migrate_huge_offline
>     - use NUMA nodes 0,1.
>     - mmap and free 8388608 bytes hugepages on node 0
>     - mmap and free 8388608 bytes hugepages on node 1
>     madvise: Cannot allocate memory
> 
>     $ cat /proc/meminfo
>     MemTotal:        4026772 kB
>     MemFree:          976300 kB
>     MemAvailable:     892840 kB
>     Buffers:           20936 kB
>     Cached:            99768 kB
>     SwapCached:         5904 kB
>     Active:            84332 kB
>     Inactive:         116328 kB
>     Active(anon):      27944 kB
>     Inactive(anon):    68524 kB
>     Active(file):      56388 kB
>     Inactive(file):    47804 kB
>     Unevictable:        7532 kB
>     Mlocked:               0 kB
>     SwapTotal:       2621436 kB
>     SwapFree:        2609844 kB
>     Dirty:                56 kB
>     Writeback:             0 kB
>     AnonPages:         81764 kB
>     Mapped:            54348 kB
>     Shmem:              8948 kB
>     KReclaimable:      22744 kB
>     Slab:              52056 kB
>     SReclaimable:      22744 kB
>     SUnreclaim:        29312 kB
>     KernelStack:        3888 kB
>     PageTables:         2804 kB
>     NFS_Unstable:          0 kB
>     Bounce:                0 kB
>     WritebackTmp:          0 kB
>     CommitLimit:     3260612 kB
>     Committed_AS:     828196 kB
>     VmallocTotal:   34359738367 kB
>     VmallocUsed:       19260 kB
>     VmallocChunk:          0 kB
>     Percpu:             5120 kB
>     HardwareCorrupted:  5368 kB
>     AnonHugePages:     18432 kB
>     ShmemHugePages:        0 kB
>     ShmemPmdMapped:        0 kB
>     FileHugePages:         0 kB
>     FilePmdMapped:         0 kB
>     CmaTotal:              0 kB
>     CmaFree:               0 kB
>     HugePages_Total:    1342     // still counted as hugetlb pages.
>     HugePages_Free:        0     // all hugepage are still allocated
> (or leaked?)
>     HugePages_Rsvd:        0
>     HugePages_Surp:      762     // some are counted in surplus.
>     Hugepagesize:       2048 kB
>     Hugetlb:         2748416 kB
>     DirectMap4k:      112480 kB
>     DirectMap2M:     4081664 kB
> 
> 
>     $ page-types -b hwpoison
>                  flags      page-count       MB  symbolic-flags
>              long-symbolic-flags
>     0x0000000000080008             421        1
> ___U_______________X_______________________      uptodate,hwpoison
>     0x00000000000a8018               1        0
> ___UD__________H_G_X_______________________
> uptodate,dirty,compound_head,huge,hwpoison
>     0x00000000000a801c             920        3
> __RUD__________H_G_X_______________________
> referenced,uptodate,dirty,compound_head,huge,hwpoison
>                  total            1342        5
> 
> This means that some hugepages are dissolved, but the others not,
> maybe which is not desirable.
> I'll dig this more later but just let me share at first.
> 
> A few minor comment below ...


Uhm, weird.

I will be taking a look today.

Thanks