linux-kernel - Re: [PATCH V4 00/10] mm: page_alloc: freelist migratetype hygiene

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Date: Wed, 27 Mar 2024 09:10:38 -0400
From: Zi Yan <ziy@...dia.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Johannes Weiner <hannes@...xchg.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Mel Gorman <mgorman@...hsingularity.net>,
 "Huang, Ying" <ying.huang@...el.com>, David Hildenbrand <david@...hat.com>,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 00/10] mm: page_alloc: freelist migratetype hygiene

On 27 Mar 2024, at 5:30, Vlastimil Babka wrote:

> On 3/20/24 7:02 PM, Johannes Weiner wrote:
>> V4:
>> - fixed !pcp_order_allowed() case in free_unref_folios()
>> - reworded the patch 0 changelog a bit for the git log
>> - rebased to mm-everything-2024-03-19-23-01
>> - runtime-tested again with various CONFIG_DEBUG_FOOs enabled
>>
>> ---
>>
>> The page allocator's mobility grouping is intended to keep unmovable
>> pages separate from reclaimable/compactable ones to allow on-demand
>> defragmentation for higher-order allocations and huge pages.
>>
>> Currently, there are several places where accidental type mixing
>> occurs: an allocation asks for a page of a certain migratetype and
>> receives another. This ruins pageblocks for compaction, which in turn
>> makes allocating huge pages more expensive and less reliable.
>>
>> The series addresses those causes. The last patch adds type checks on
>> all freelist movements to prevent new violations being introduced.
>>
>> The benefits can be seen in a mixed workload that stresses the machine
>> with a memcache-type workload and a kernel build job while
>> periodically attempting to allocate batches of THP. The following data
>> is aggregated over 50 consecutive defconfig builds:
>
> Great stuff. What would you say to the following on top?
>
> ----8<----
> From 84f8a6d3a9e34c7ed8b438c3152d56e359a4ffb4 Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@...e.cz>
> Date: Wed, 27 Mar 2024 10:19:47 +0100
> Subject: [PATCH] mm: page_alloc: change move_freepages() to
>  __move_freepages_block()
>
> The function is now supposed to be called only on a single pageblock and
> checks start_pfn and end_pfn accordingly. Rename it to make this more
> obvious and drop the end_pfn parameter which can be determined trivially
> and none of the callers use it for anything else.
>
> Also make the (now internal) end_pfn exclusive, which is more common.
>
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> ---
>  mm/page_alloc.c | 43 ++++++++++++++++++++-----------------------
>  1 file changed, 20 insertions(+), 23 deletions(-)
>
This looks good to me and makes sense. Reviewed-by: Zi Yan <ziy@...dia.com>

--
Best Regards,
Yan, Zi

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