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SubjectRe: [PATCH -mm] mm, huge page: Copy to access sub-page last when copy huge page
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On 05/17/2018 11:24 PM, Michal Hocko wrote:
> On Fri 18-05-18 11:03:16, Huang, Ying wrote:
> [...]
>> The patch is a generic optimization which should benefit quite some
>> workloads, not for a specific use case. To demonstrate the performance
>> benefit of the patch, we tested it with vm-scalability run on
>> transparent huge page.
>
> It is also adds quite some non-intuitive code. So is this worth? Does
> any _real_ workload benefits from the change?

One way to 'add less code' would be to create a helper routine that
indicates the order in which sub-pages are to be copied. IIUC, you
added the same algorithm for sub-page ordering to copy_huge_page()
that was previously added to clear_huge_page(). Correct? If so,
then perhaps a common helper could be used by both the clear and copy
huge page routines. It would also make maintenance easier.

--
Mike Kravetz

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