On Wed 22-11-17 10:09:13, Zi Yan wrote:

Michal Hocko wrote:

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On Wed 22-11-17 09:43:46, Zi Yan wrote:

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Michal Hocko wrote:

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but why is unsafe to enable the feature on other arches which support THP? Is there any plan to do the next step and remove this config option?

Because different architectures have their own way of specifying a swap entry. This means, to support THP migration, each architecture needs to add its own __pmd_to_swp_entry() and __swp_entry_to_pmd(), which are used for arch-independent pmd_to_swp_entry() and swp_entry_to_pmd().

I understand that part. But this smells like a matter of coding, no? I was suprised to see the note about safety which didn't make much sense to me.

And testing as well. I had powerpc book3s support in my initial patch submission, but removed it because I do not have access to the powerpc machine any more. I also tried ARM64, which seems working by adding the code, but I have no hardware to test it now.

Any suggestions?

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