On Thu 08-12-16 17:36:24, Huang Shijie wrote:

On Wed, Dec 07, 2016 at 11:02:38PM +0800, Michal Hocko wrote:

[...]

quoted

I haven't yet checked your patchset but I can tell you one thing.

Could you please review the patch set when you have time? Thanks a lot.

From a quick glance you do not handle the reservation code at all. You

just make sure that the allocation doesn't fail unconditionally. I might
be wrong here and Naoya resp. Mike will know much better but this seems
far from enough to me.

quoted

Surplus and subpool pages code is tricky as hell. And it is not just a

Agree. 

Do we really need so many accountings? such as reserve/ovorcommit/surplus.

If we want to make giga page the first class citizen then the whole
reservation/surplus code has to independent on the page size.

quoted

matter of teaching the huge page allocation code to do the right thing.
There are subtle details all over the place. E.g. we currently
do not free giga pages AFAICS. In fact I believe that the giga pages are

Please correct me if I am wrong. :)

I think the free-giga-pages can work well.
Please see the code in update_and_free_page(). 

Hmm, I have missed that part. I guess you are right but I would have to
look much closer. Hugetlb code tends to be full of surprises.

Could you please list all the subtle details you think the code is wrong?
I can check them one by one.

Well, this would take me quite some time and basically restudy the whole
hugetlb code again. What you are trying to achieve is not a simple "fix
a test case" thing. You are trying to implement full featured giga pages
suport. And as I've said this requires a deeper understanding of the
current code and clean it up considerably wrt. giga pages. This is
definitely desirable plan longterm and I would like to encourage you for
that but it is not a simple project at the same time. 
-- 
Michal Hocko
SUSE Labs