linux-kernel - Re: [PATCH v4 12/15] mm,hwpoison: Rework soft offline for in-use pages

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Date:   Wed, 22 Jul 2020 10:08:59 +0200
From:   osalvador@...e.de
To:     HORIGUCHI NAOYA(堀口　直也) <naoya.horiguchi@....com>
Cc:     akpm@...ux-foundation.org, Michal Hocko <MHocko@...e.com>,
        linux-mm@...ck.org, mike.kravetz@...cle.com, david@...hat.com,
        aneesh.kumar@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
        Oscar Salvador <OSalvador@...e.com>
Subject: Re: [PATCH v4 12/15] mm,hwpoison: Rework soft offline for in-use
 pages

On 2020-07-20 10:27, osalvador@...e.de wrote:
> 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.

After some digging up I __think__ I found the problem.
I will try to fix it up and I will be running tests.

I might reach out to you once I am done because I remember you had a 
test-suite that worked quite well, so you can give it a spin there.

Thanks