On Wed 22-11-17 10:09:13, Zi Yan wrote: > > > Michal Hocko wrote: > > On Wed 22-11-17 09:43:46, Zi Yan wrote: > >> > >> Michal Hocko wrote: [...] > >>> 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? Cc arch maintainers and mailing lists? -- Michal Hocko SUSE Labs