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

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Date: Mon, 19 Feb 2024 21:31:30 -0500
From: Zi Yan <ziy@...dia.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: 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>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 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 19 Feb 2024, at 21:06, Andrew Morton wrote:

> On Fri, 16 Feb 2024 12:04:28 -0500 Zi Yan <zi.yan@...t.com> wrote:
>
>> Baolin's patch
>
> Baolin writes many patches and patches have names, please use them!
Sorry for not being specific. I mean this fixup:
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?h=mm-everything-2024-02-16-01-35&id=97f749c7c82f677f89bbf4f10de7816ce9b071fe

to this patch:
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?h=mm-everything-2024-02-16-01-35&id=ea87b0558293a5ad597bea606fe261f7b2650cda

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.

>> diff --git a/mm/compaction.c b/mm/compaction.c
>> index 01ec85cfd623f..e60135e2019d6 100644
>> --- a/mm/compaction.c
>> +++ b/mm/compaction.c
>> @@ -1798,7 +1798,7 @@ static struct folio *compaction_alloc(struct folio *src, unsigned long data)
>>  	dst = list_entry(cc->freepages.next, struct folio, lru);
>>  	list_del(&dst->lru);
>>  	cc->nr_freepages--;
>> -	cc->nr_migratepages -= 1 << order;
>> +	cc->nr_migratepages--;
>>
>>  	return dst;
>>  }
>> @@ -1814,7 +1814,7 @@ static void compaction_free(struct folio *dst, unsigned long data)
>>
>>  	list_add(&dst->lru, &cc->freepages);
>>  	cc->nr_freepages++;
>> -	cc->nr_migratepages += 1 << order;
>> +	cc->nr_migratepages++;
>>  }

--
Best Regards,
Yan, Zi

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