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Date: Tue, 20 Feb 2024 10:11:46 +0100
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Subject: Re: [PATCH v6 2/4] mm/compaction: enable compacting >0 order folios.
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From: David Hildenbrand <david@redhat.com>
To: Zi Yan <ziy@nvidia.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: "Huang, Ying" <ying.huang@intel.com>, Ryan Roberts
 <ryan.roberts@arm.com>, Andrew Morton <akpm@linux-foundation.org>,
 "Matthew Wilcox (Oracle)" <willy@infradead.org>,
 "Yin, Fengwei" <fengwei.yin@intel.com>, Yu Zhao <yuzhao@google.com>,
 Vlastimil Babka <vbabka@suse.cz>,
 "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
 Johannes Weiner <hannes@cmpxchg.org>,
 Baolin Wang <baolin.wang@linux.alibaba.com>,
 Kemeng Shi <shikemeng@huaweicloud.com>,
 Mel Gorman <mgorman@techsingularity.net>, Rohan Puri
 <rohan.puri15@gmail.com>, Mcgrof Chamberlain <mcgrof@kernel.org>,
 Adam Manzanares <a.manzanares@samsung.com>,
 "Vishal Moola (Oracle)" <vishal.moola@gmail.com>
References: <20240216170432.1268753-1-zi.yan@sent.com>
 <20240216170432.1268753-3-zi.yan@sent.com>
 <416d1450-6480-4113-b778-689a8f1d4e42@redhat.com>
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In-Reply-To: <416d1450-6480-4113-b778-689a8f1d4e42@redhat.com>
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On 20.02.24 10:03, David Hildenbrand wrote:
> On 16.02.24 18:04, Zi Yan wrote:
>> From: Zi Yan <ziy@nvidia.com>
>>
>> migrate_pages() supports >0 order folio migration and during compaction,
>> even if compaction_alloc() cannot provide >0 order free pages,
>> migrate_pages() can split the source page and try to migrate the base
>> pages from the split.  It can be a baseline and start point for adding
>> support for compacting >0 order folios.
>>
>> Signed-off-by: Zi Yan <ziy@nvidia.com>
>> Suggested-by: Huang Ying <ying.huang@intel.com>
>> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>> Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> Tested-by: Yu Zhao <yuzhao@google.com>
>> Cc: Adam Manzanares <a.manzanares@samsung.com>
>> Cc: David Hildenbrand <david@redhat.com>
>> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> Cc: Kemeng Shi <shikemeng@huaweicloud.com>
>> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>> Cc: Luis Chamberlain <mcgrof@kernel.org>
>> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
>> Cc: Mel Gorman <mgorman@techsingularity.net>
>> Cc: Ryan Roberts <ryan.roberts@arm.com>
>> Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
>> Cc: Vlastimil Babka <vbabka@suse.cz>
>> Cc: Yin Fengwei <fengwei.yin@intel.com>
>> ---
>>    mm/compaction.c | 66 ++++++++++++++++++++++++++++++++++++++-----------
>>    1 file changed, 52 insertions(+), 14 deletions(-)
>>
>> diff --git a/mm/compaction.c b/mm/compaction.c
>> index cc801ce099b4..aa6aad805c4d 100644
>> --- a/mm/compaction.c
>> +++ b/mm/compaction.c
>> @@ -816,6 +816,21 @@ static bool too_many_isolated(struct compact_control *cc)
>>    	return too_many;
>>    }
>>    
>> +/*
> 
> 
> Can't you add these comments to the respective checks? Like
> 
> static bool skip_isolation_on_order(int order, int target_order)
> {
> 	/*
> 	 * Unless we are performing global compaction (targert_order <
> 	 * 0), skip any folios that are larger than the target order: we
> 	 * wouldn't be here if we'd have a free folio with the desired
> 	 * target_order, so migrating this folio would likely fail
> 	 * later.
> 	 */
> 	if (target_order != -1 && order >= target_order)
> 		return true;

I just stumbled over "is_via_compact_memory", likely that should be used 
instead of the "!= -1 check.

-- 
Cheers,

David / dhildenb