On 06/03/2015 07:06 PM, Kirill A. Shutemov wrote:
The patch updates Documentation/vm/transhuge.txt to reflect changes in
THP design.
One thing I'm missing is info about the deferred splitting.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
Documentation/vm/transhuge.txt | 124 +++++++++++++++++++++++------------------
1 file changed, 69 insertions(+), 55 deletions(-)
diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt
index 6b31cfbe2a9a..2352b12cae93 100644
--- a/Documentation/vm/transhuge.txt
+++ b/Documentation/vm/transhuge.txt
@@ -35,10 +35,10 @@ miss is going to run faster.
== Design ==
-- "graceful fallback": mm components which don't have transparent
- hugepage knowledge fall back to breaking a transparent hugepage and
- working on the regular pages and their respective regular pmd/pte
- mappings
+- "graceful fallback": mm components which don't have transparent hugepage
+ knowledge fall back to breaking huge pmd mapping into table of ptes and,
+ if nesessary, split a transparent hugepage. Therefore these components
necessary
+
+split_huge_page uses migration entries to stabilize page->_count and
+page->_mapcount.
Hm, what if there's some physical memory scanner taking page->_count
pins? I think compaction shouldn't be an issue, but maybe some others?
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