Re: [PATCH RFC 2/4] mm/page_alloc: place pages to tail in __putback_isolated_page()

David Hildenbrand
2020-09-18T07:27:38Z

On 18.09.20 04:07, Wei Yang wrote:
> On Wed, Sep 16, 2020 at 08:34:09PM +0200, David Hildenbrand wrote:
>> __putback_isolated_page() already documents that pages will be placed to
>> the tail of the freelist - this is, however, not the case for
>> "order >= MAX_ORDER - 2" (see buddy_merge_likely()) - which should be
>> the case for all existing users.
>>
>> This change affects two users:
>> - free page reporting
>> - page isolation, when undoing the isolation.
>>
>> This behavior is desireable for pages that haven't really been touched
>> lately, so exactly the two users that don't actually read/write page
>> content, but rather move untouched pages.
>>
>> The new behavior is especially desirable for memory onlining, where we
>> allow allocation of newly onlined pages via undo_isolate_page_range()
>> in online_pages(). Right now, we always place them to the head of the
>
> The code looks good, while I don't fully understand the log here.
>
> undo_isolate_page_range() is used in __offline_pages and alloc_contig_range. I
> don't connect them with online_pages(). Do I miss something?

Yeah, please look at -mm / -next instead. See

https://lkml.kernel.org/r/20200819175957.28465-11-david@redhat.com

--
Thanks,

David / dhildenb