Re: [RFC PATCH v2 00/30] 1GB PUD THP support on x86_64

[David Hildenbrand]

>>> - huge page sizes controllable by the userspace?
>>
>> It might be good to allow advanced users to choose the page sizes, so they
>> have better control of their applications.
> 
> Could you elaborate more? Those advanced users can use hugetlb, right?
> They get a very good control over page size and pool preallocation etc.
> So they can get what they need - assuming there is enough memory.
> 

I am still not convinced that 1G THP (TGP :) ) are really what we want
to support. I can understand that there are some use cases that might
benefit from it, especially:

"I want a lot of memory, give me memory in any granularity you have, I
absolutely don't care - but of course, more TGP might be good for
performance." Say, you want a 5GB region, but only have a single 1GB
hugepage lying around. hugetlbfs allocation will fail.


But then, do we really want to optimize for such (very special?) use
cases via " 58 files changed, 2396 insertions(+), 460 deletions(-)" ?

I think gigantic pages are a sparse resource. Only selected applications
*really* depend on them and benefit from them. Let these special
applications handle it explicitly.

Can we have a summary of use cases that would really benefit from this
change?

-- 
Thanks,

David / dhildenb