Re: [PATCH v1] mm/madvise: update comment on sys_madvise()

On Wed, Jan 27, 2016 at 04:28:35PM +0100, Michal Hocko wrote:

On Wed 27-01-16 10:24:25, Naoya Horiguchi wrote:

quoted

Some new MADV_* advices are not documented in sys_madvise() comment.
So let's update it.

Signed-off-by: Naoya Horiguchi <redacted>

Other than few suggestions below
Acked-by: Michal Hocko <mhocko@suse.com>

quoted

---
 mm/madvise.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git v4.4-mmotm-2016-01-20-16-10/mm/madvise.c v4.4-mmotm-2016-01-20-16-10_patched/mm/madvise.c
index 6a77114..c897b15 100644
--- v4.4-mmotm-2016-01-20-16-10/mm/madvise.c
+++ v4.4-mmotm-2016-01-20-16-10_patched/mm/madvise.c

@@ -639,14 +639,26 @@ madvise_behavior_valid(int behavior)
  *		some pages ahead.
  *  MADV_DONTNEED - the application is finished with the given range,
  *		so the kernel can free resources associated with it.
+ *  MADV_FREE - the application marks pages in the given range as lasyfree,

s@lasyfree@lazy free@

quoted

+ *		where actual purges are postponed until memory pressure happens.
  *  MADV_REMOVE - the application wants to free up the given range of
  *		pages and associated backing store.
  *  MADV_DONTFORK - omit this area from child's address space when forking:
  *		typically, to avoid COWing pages pinned by get_user_pages().
  *  MADV_DOFORK - cancel MADV_DONTFORK: no longer omit this area when forking.
+ *  MADV_HWPOISON - trigger memory error handler as if the given memory range
+ *		were corrupted by unrecoverable hardware memory failure.
+ *  MADV_SOFT_OFFLINE - try to soft-offline the given range of memory.
  *  MADV_MERGEABLE - the application recommends that KSM try to merge pages in
  *		this area with pages of identical content from other such areas.
  *  MADV_UNMERGEABLE- cancel MADV_MERGEABLE: no longer merge pages with others.
+ *  MADV_HUGEPAGE - the application wants to allocate transparent hugepages to
+ *		load the content of the given memory range.

I guess that a slightly different wording would be better:

application wants to back the given range by transparent huge pages in
the future. Existing pages might be coalesced and new pages might be
allocated as THP.

quoted

+ *  MADV_NOHUGEPAGE - cancel MADV_HUGEPAGE: no longer allocate transparent
+ *		hugepages.

Mark the given range as not worth being backed by transparent huge pages
so neither existing pages will be coalesced into THP nor new pages will
be allocated as THP.

Thank you for the elaboration.
I'm fine for all these change.

- Naoya
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