linux-kernel - Re: [PATCH RFC 2/4] mm/page_alloc: place pages to tail in __putback_isolated

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Message-ID: <20200921015700.GA83969@L-31X9LVDL-1304.local>
Date:   Mon, 21 Sep 2020 09:57:00 +0800
From:   Wei Yang <richard.weiyang@...ux.alibaba.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Wei Yang <richard.weiyang@...ux.alibaba.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-hyperv@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linux-acpi@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Oscar Salvador <osalvador@...e.de>,
        Mike Rapoport <rppt@...nel.org>,
        Scott Cheloha <cheloha@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH RFC 2/4] mm/page_alloc: place pages to tail in
 __putback_isolated_page()

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
Help you, Help me