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

Wei Yang
2020-09-21T01:57:07Z

On Fri, Sep 18, 2020 at 09:27:23AM +0200, David Hildenbrand wrote:
>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, I get the point.

>
>--
>Thanks,
>
>David / dhildenb

--
Wei Yang
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