[PATCH] doc: mm: migration doesn't use FOLL_SPLIT anymore

[PATCH] doc: mm: migration doesn't use FOLL_SPLIT anymore

[Yang Shi]

When demonstrating FOLL_SPLIT in transhuge document, migration is used
as an example.  But, since commit 94723aafb9e7 ("mm: unclutter THP
migration"), the way of THP migration is totally changed.  FOLL_SPLIT is
not used by migration anymore due to the change.

Remove the obsolete example to avoid confusion.

Cc: Michal Hocko <mhocko@suse.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
---
 Documentation/vm/transhuge.rst | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/Documentation/vm/transhuge.rst b/Documentation/vm/transhuge.rst
index a8cf680..8df3806 100644
--- a/Documentation/vm/transhuge.rst
+++ b/Documentation/vm/transhuge.rst
@@ -55,13 +55,7 @@ prevent page from being split by anyone.
 In case you can't handle compound pages if they're returned by
 follow_page, the FOLL_SPLIT bit can be specified as parameter to
 follow_page, so that it will split the hugepages before returning
-them. Migration for example passes FOLL_SPLIT as parameter to
-follow_page because it's not hugepage aware and in fact it can't work
-at all on hugetlbfs (but it instead works fine on transparent
-hugepages thanks to FOLL_SPLIT). migration simply can't deal with
-hugepages being returned (as it's not only checking the pfn of the
-page and pinning it during the copy but it pretends to migrate the
-memory in regular page sizes and with regular pte/pmd mappings).
+them.
 
 Graceful fallback
 =================
-- 
1.8.3.1

Re: [PATCH] doc: mm: migration doesn't use FOLL_SPLIT anymore

[Zi Yan]

On 18 Apr 2019, at 16:17, Yang Shi wrote:

> When demonstrating FOLL_SPLIT in transhuge document, migration is used
> as an example.  But, since commit 94723aafb9e7 ("mm: unclutter THP
> migration"), the way of THP migration is totally changed.  FOLL_SPLIT 
> is
> not used by migration anymore due to the change.
>
> Remove the obsolete example to avoid confusion.
>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Zi Yan <ziy@nvidia.com>
> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
> ---
>  Documentation/vm/transhuge.rst | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/Documentation/vm/transhuge.rst 
> b/Documentation/vm/transhuge.rst
> index a8cf680..8df3806 100644
> --- a/Documentation/vm/transhuge.rst
> +++ b/Documentation/vm/transhuge.rst
> @@ -55,13 +55,7 @@ prevent page from being split by anyone.
>  In case you can't handle compound pages if they're returned by
>  follow_page, the FOLL_SPLIT bit can be specified as parameter to
>  follow_page, so that it will split the hugepages before returning
> -them. Migration for example passes FOLL_SPLIT as parameter to
> -follow_page because it's not hugepage aware and in fact it can't work
> -at all on hugetlbfs (but it instead works fine on transparent
> -hugepages thanks to FOLL_SPLIT). migration simply can't deal with
> -hugepages being returned (as it's not only checking the pfn of the
> -page and pinning it during the copy but it pretends to migrate the
> -memory in regular page sizes and with regular pte/pmd mappings).
> +them.
>
>  Graceful fallback
>  =================
> -- 
> 1.8.3.1

Thanks for updating the document.

Reviewed-by: Zi Yan <ziy@nvidia.com>



--
Best Regards,
Yan Zi

Re: [PATCH] doc: mm: migration doesn't use FOLL_SPLIT anymore

[Jonathan Corbet]

On Fri, 19 Apr 2019 04:17:04 +0800
Yang Shi <yang.shi@linux.alibaba.com> wrote:

> When demonstrating FOLL_SPLIT in transhuge document, migration is used
> as an example.  But, since commit 94723aafb9e7 ("mm: unclutter THP
> migration"), the way of THP migration is totally changed.  FOLL_SPLIT is
> not used by migration anymore due to the change.
> 
> Remove the obsolete example to avoid confusion.
> 
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Zi Yan <ziy@nvidia.com>
> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>

Applied, thanks.

jon