Re: [PATCH v2 1/2] mm/page_alloc: conditionally split > pageblock_order pages in free_one_page() and move_freepages_block_isolate()

[David Hildenbrand <david@redhat.com>]

>> Having a function guess the caller is a bit of an anti-pattern. The
>> resulting code is hard to follow, and it's very easy to
>> unintentionally burden some cases with unnecessary stuff. It's better
>> to unshare paths until you don't need conditionals like this.
>   > > In addition to the fastpath, I think you're also punishing the
>> move_freepages_block_isolate() case. We *know* we just changed the
>> type of one of the buddy's blocks, and yet you're still checking the
>> the range again to decide whether to split.
> 
> Yes, that's not ideal, and it would be easy to unshare that case (call
> the "split" function instead of a "maybe_split" function).
> 
> I am not 100% sure though, if move_freepages_block_isolate() can always
> decide "I really have a mixture", but that code is simply quite advanced :)

I played with it, and I think we can indeed assume that 
move_freepages_block_isolate() will always have to split.

-- 
Cheers,

David / dhildenb