Re: [PATCH v1] mm/madvise: update comment on sys_madvise()
From: Michal Hocko
Date: Wed Jan 27 2016 - 10:28:52 EST
On Wed 27-01-16 10:24:25, Naoya Horiguchi wrote:
> Some new MADV_* advices are not documented in sys_madvise() comment.
> So let's update it.
> Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Other than few suggestions below
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> 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,
> + * 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.
> + * 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.
> + * MADV_DONTDUMP - the application wants to prevent pages in the given range
> + * from being included in its core dump.
> + * MADV_DODUMP - cancel MADV_DONTDUMP: no longer exclude from core dump.
> * return values:
> * zero - success
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