On 08/11/16 10:31, Naoya Horiguchi wrote: > Hi everyone, > > I've updated thp migration patches for v4.9-rc2-mmotm-2016-10-27-18-27 > with feedbacks for ver.1. > > General description (no change since ver.1) > =========================================== > > This patchset enhances page migration functionality to handle thp migration > for various page migration's callers: > - mbind(2) > - move_pages(2) > - migrate_pages(2) > - cgroup/cpuset migration > - memory hotremove > - soft offline > > The main benefit is that we can avoid unnecessary thp splits, which helps us > avoid performance decrease when your applications handles NUMA optimization on > their own. > > The implementation is similar to that of normal page migration, the key point > is that we modify a pmd to a pmd migration entry in swap-entry like format. > > Changes / Notes > =============== > > - pmd_present() in x86 checks _PAGE_PRESENT, _PAGE_PROTNONE and _PAGE_PSE > bits together, which makes implementing thp migration a bit hard because > _PAGE_PSE bit is currently used by soft-dirty in swap-entry format. > I was advised to dropping _PAGE_PSE in pmd_present(), but I don't think > of the justification, so I keep it in this version. Instead, my approach > is to move _PAGE_SWP_SOFT_DIRTY to bit 6 (unused) and reserve bit 7 for > pmd non-present cases. Thanks, IIRC pmd_present = _PAGE_PRESENT | _PAGE_PROTNONE | _PAGE_PSE AutoNUMA balancing would change it to pmd_present = _PAGE_PROTNONE | _PAGE_PSE and PMD_SWP_SOFT_DIRTY would make it pmd_present = _PAGE_PSE What you seem to be suggesting in your comment is that pmd_present should be _PAGE_PRESENT | _PAGE_PROTNONE Isn't that good enough? For THP migration I guess we use _PAGE_PRESENT | _PAGE_PROTNONE | is_migration_entry(pmd) > > - this patchset still covers only x86_64. Zi Yan posted a patch for ppc64 > and I think it's favorably received so that's fine. But there's unsolved > minor suggestion by Aneesh, so I don't include it in this set, expecting > that it will be updated/reposted. > > - pte-mapped thp and doubly-mapped thp were not supported in ver.1, but > this version should work for such kinds of thp. > > - thp page cache is not tested yet, and it's at the head of my todo list > for future version. > > Any comments or advices are welcomed. Balbir Singh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>