[PATCH 3/3] mm: migrate: Stabilise page count when migrating transparent hugepages

2017-06-06 Thread Will Deacon
When migrating a transparent hugepage, migrate_misplaced_transhuge_page guards itself against a concurrent fastgup of the page by checking that the page count is equal to 2 before and after installing the new pmd. If the page count changes, then the pmd is reverted back to the original entry, howe

Re: [PATCH 3/3] mm: migrate: Stabilise page count when migrating transparent hugepages

2017-06-08 Thread Kirill A. Shutemov
On Tue, Jun 06, 2017 at 06:58:36PM +0100, Will Deacon wrote: > When migrating a transparent hugepage, migrate_misplaced_transhuge_page > guards itself against a concurrent fastgup of the page by checking that > the page count is equal to 2 before and after installing the new pmd. > > If the page c

Re: [PATCH 3/3] mm: migrate: Stabilise page count when migrating transparent hugepages

2017-06-08 Thread Vlastimil Babka
On 06/06/2017 07:58 PM, Will Deacon wrote: > When migrating a transparent hugepage, migrate_misplaced_transhuge_page > guards itself against a concurrent fastgup of the page by checking that > the page count is equal to 2 before and after installing the new pmd. > > If the page count changes, then

Re: [PATCH 3/3] mm: migrate: Stabilise page count when migrating transparent hugepages

2017-06-08 Thread Will Deacon
On Thu, Jun 08, 2017 at 12:52:07PM +0200, Vlastimil Babka wrote: > On 06/06/2017 07:58 PM, Will Deacon wrote: > > When migrating a transparent hugepage, migrate_misplaced_transhuge_page > > guards itself against a concurrent fastgup of the page by checking that > > the page count is equal to 2 befo

Re: [PATCH 3/3] mm: migrate: Stabilise page count when migrating transparent hugepages

2017-06-09 Thread zhong jiang
On 2017/6/8 20:07, Will Deacon wrote: > On Thu, Jun 08, 2017 at 12:52:07PM +0200, Vlastimil Babka wrote: >> On 06/06/2017 07:58 PM, Will Deacon wrote: >>> When migrating a transparent hugepage, migrate_misplaced_transhuge_page >>> guards itself against a concurrent fastgup of the page by checking t

Re: [PATCH 3/3] mm: migrate: Stabilise page count when migrating transparent hugepages

2017-06-09 Thread zhong jiang
On 2017/6/8 20:07, Will Deacon wrote: > On Thu, Jun 08, 2017 at 12:52:07PM +0200, Vlastimil Babka wrote: >> On 06/06/2017 07:58 PM, Will Deacon wrote: >>> When migrating a transparent hugepage, migrate_misplaced_transhuge_page >>> guards itself against a concurrent fastgup of the page by checking t