On 11/10/2016 07:31 PM, Zi Yan wrote: > On 9 Nov 2016, at 18:52, Naoya Horiguchi wrote: > >> 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. > > Migrating 4KB pages has much lower (~1/3) throughput than 2MB pages. I assume the 2MB throughput you mentioned is with this THP migration feature enabled. > > What I get is that on average it takes 1987.38 us to migrate 512 4KB pages and > 658.54 us to migrate 1 2MB page. > > I did the test in a two-socket Intel Xeon E5-2640v4 box. I used migrate_pages() > system call to migrate pages. MADV_NOHUGEPAGE and MADV_HUGEPAGE are used to > make 4KB and 2MB pages and each page’s flags are checked to make sure the page > size is 4KB or 2MB THP. > > There is no split page. But the page migration time already tells the story. Right. Just wondering if we can add a test case which measures just this migration time improvement by avoiding the split not the TLB based improvement which the workload will receive as an addition. -- 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>
