On 09/21/2016 05:05 AM, Michal Hocko wrote:
> On Tue 20-09-16 10:43:13, Dave Hansen wrote:
>> On 09/20/2016 08:52 AM, Rui Teng wrote:
>>> On 9/20/16 10:53 PM, Dave Hansen wrote:
>>>> That's good, but aren't we still left with a situation where we've
>>>> offlined and dissolved the _middle_ of a gigantic huge page while the
>>>> head page is still in place and online?
>>>> That seems bad.
>>> What about refusing to change the status for such memory block, if it
>>> contains a huge page which larger than itself? (function
>> How will this be visible to users, though? That sounds like you simply
>> won't be able to offline memory with gigantic huge pages.
> I might be missing something but Is this any different from a regular
> failure when the memory cannot be freed? I mean
> /sys/devices/system/memory/memory API doesn't give you any hint whether
> the memory in the particular block is used and
It's OK to have free hugetlbfs pages in an area that's being offline'd.
If we did that, it would not be OK to have a free gigantic hugetlbfs
page that's larger than the area being offlined.
It would be a wee bit goofy to have the requirement that userspace go
find all the gigantic pages and make them non-gigantic before trying to