linux-kernel - Re: [PATCH v6 0/4] Enable >0 order folio memory compaction

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Date: Tue, 20 Feb 2024 14:28:10 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Zi Yan <ziy@...dia.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, "Huang, Ying" <ying.huang@...el.com>,
 Ryan Roberts <ryan.roberts@....com>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>,
 David Hildenbrand <david@...hat.com>, "Yin, Fengwei"
 <fengwei.yin@...el.com>, Yu Zhao <yuzhao@...gle.com>,
 Vlastimil Babka <vbabka@...e.cz>,
 "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
 Johannes Weiner <hannes@...xchg.org>, Kemeng Shi
 <shikemeng@...weicloud.com>, Mel Gorman <mgorman@...hsingularity.net>,
 Rohan Puri <rohan.puri15@...il.com>, Mcgrof Chamberlain <mcgrof@...nel.org>,
 Adam Manzanares <a.manzanares@...sung.com>,
 "Vishal Moola (Oracle)" <vishal.moola@...il.com>
Subject: Re: [PATCH v6 0/4] Enable >0 order folio memory compaction

On 2024/2/20 11:30, Andrew Morton wrote:
> On Tue, 20 Feb 2024 11:00:39 +0800 Baolin Wang <baolin.wang@...ux.alibaba.com> wrote:
> 
>>> The patch was based on top of my early version of this patchset, thus
>>> uses "cc->nr_migratepages -= 1 << order;" and
>>> "cc->nr_migratepages += 1 << order;", but now it is applied before
>>> mine. The change should be "cc->nr_migratepages--;" and
>>> "cc->nr_migratepages++;", respectively.
>>>
>>>>
>>>>> on nr_migratepages was based on this one, a better fixup
>>>>> for it might be below. Since before my patchset, compaction only deals with
>>>>> order-0 pages.
>>>>
>>>> I don't understand what this means.  The patchset you sent applies OK
>>>> to mm-unstable so what else is there to do?
>>>
>>> Your above fixup to Baolin's patch needs to be changed to the patch below
>>> and my "mm/compaction: add support for >0 order folio memory compaction" will
>>> need to be adjusted accordingly to be applied on top.
>>>
>>> Let me know if anything is unclear.
>>
>> Hi Andrew,
>>
>> To avoid conflicts, you can drop these two patches, and I will send a
>> new version with fixing the issue pointed by Vlastimilb on top of
>> "mm/compaction: add support for >0 order folio memory compaction".
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?h=mm-everything-2024-02-16-01-35&id=97f749c7c82f677f89bbf4f10de7816ce9b071fe
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?h=mm-everything-2024-02-16-01-35&id=ea87b0558293a5ad597bea606fe261f7b2650cda
> 
> Well I thought I'd fixed everything up 10 minutes ago.  Please take a
> look at next mm-unstable.

Sure. And I found a minor rebase error in the compaction_alloc() 
function while Zi Yan's original patch is correct.

+	cc->nr_freepages -= 1 << order;
  	cc->nr_migratepages--;
-
-	return dst;
+	return page_rmappable_folio(&dst->page);
  }

should change to be:
cc->nr_migratepages -= 1 << order;