Hi Anshuman, On Wed, Nov 09, 2016 at 04:03:04PM +0530, Anshuman Khandual wrote: > On 11/08/2016 05:01 AM, 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. > > Will it be better to have new THP_MIGRATE_SUCCESS and THP_MIGRATE_FAIL > VM events to capture how many times the migration worked without first > splitting the huge page and how many time it did not work ?
Thank you for the suggestion. I think that's helpful, so will try it in next version. > Also do you > have a test case which demonstrates this THP migration and kind of shows > its better than the present split and move method ? I don't have test cases which compare thp migration and split-then-migration with some numbers. Maybe measuring/comparing the overhead of migration is a good start point, although I think the real benefit of thp migration comes from workload "after migration" by avoiding thp split. Thanks, Naoya Horiguchi
