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SubjectRe: [PATCH -V6 00/21] swap: Swapout/swapin THP in one piece
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Daniel Jordan <daniel.m.jordan@oracle.com> writes:

> On Wed, Oct 24, 2018 at 11:31:42AM +0800, Huang, Ying wrote:
>> Hi, Daniel,
>>
>> Daniel Jordan <daniel.m.jordan@oracle.com> writes:
>>
>> > On Wed, Oct 10, 2018 at 03:19:03PM +0800, Huang Ying wrote:
>> >> And for all, Any comment is welcome!
>> >>
>> >> This patchset is based on the 2018-10-3 head of mmotm/master.
>> >
>> > There seems to be some infrequent memory corruption with THPs that have been
>> > swapped out: page contents differ after swapin.
>>
>> Thanks a lot for testing this! I know there were big effort behind this
>> and it definitely will improve the quality of the patchset greatly!
>
> You're welcome! Hopefully I'll have more results and tests to share in the
> next two weeks.
>
>>
>> > Reproducer at the bottom. Part of some tests I'm writing, had to separate it a
>> > little hack-ily. Basically it writes the word offset _at_ each word offset in
>> > a memory blob, tries to push it to swap, and verifies the offset is the same
>> > after swapin.
>> >
>> > I ran with THP enabled=always. THP swapin_enabled could be always or never, it
>> > happened with both. Every time swapping occurred, a single THP-sized chunk in
>> > the middle of the blob had different offsets. Example:
>> >
>> > ** > word corruption gap
>> > ** corruption detected 14929920 bytes in (got 15179776, expected 14929920) **
>> > ** corruption detected 14929928 bytes in (got 15179784, expected 14929928) **
>> > ** corruption detected 14929936 bytes in (got 15179792, expected 14929936) **
>> > ...pattern continues...
>> > ** corruption detected 17027048 bytes in (got 15179752, expected 17027048) **
>> > ** corruption detected 17027056 bytes in (got 15179760, expected 17027056) **
>> > ** corruption detected 17027064 bytes in (got 15179768, expected 17027064) **
>>
>> 15179776 < 15179xxx <= 17027064
>>
>> 15179776 % 4096 = 0
>>
>> And 15179776 = 15179768 + 8
>>
>> So I guess we have some alignment bug. Could you try the patches
>> attached? It deal with some alignment issue.
>
> That fixed it. And removed three lines of code. Nice :)

Thanks! I will merge the fixes into the patchset.

Best Regards,
Huang, Ying

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