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

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Message-ID: <20240327142916.GD229434@cmpxchg.org>
Date: Wed, 27 Mar 2024 10:29:16 -0400
From: Johannes Weiner <hannes@...xchg.org>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...hsingularity.net>, Zi Yan <ziy@...dia.com>,
	"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 Wed, Mar 27, 2024 at 10:30:30AM +0100, 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>

Nice, that's better.

Acked-by: Johannes Weiner <hannes@...xchg.org>