linux-kernel - Re: [PATCH v5 3/3] mm/compaction: optimize >0 order folio compaction with free page split.

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Message-ID: <f7aa107d-600f-4ef0-a93d-970b3bb56c39@suse.cz>
Date: Thu, 15 Feb 2024 17:52:24 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Zi Yan <ziy@...dia.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: "Huang, Ying" <ying.huang@...el.com>, Ryan Roberts
 <ryan.roberts@....com>, Andrew Morton <akpm@...ux-foundation.org>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>,
 David Hildenbrand <david@...hat.com>, "Yin, Fengwei"
 <fengwei.yin@...el.com>, Yu Zhao <yuzhao@...gle.com>,
 "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 v5 3/3] mm/compaction: optimize >0 order folio compaction
 with free page split.

On 2/14/24 23:04, Zi Yan wrote:
> From: Zi Yan <ziy@...dia.com>
> 
> During migration in a memory compaction, free pages are placed in an array
> of page lists based on their order.  But the desired free page order
> (i.e., the order of a source page) might not be always present, thus
> leading to migration failures and premature compaction termination.  Split
> a high order free pages when source migration page has a lower order to
> increase migration successful rate.
> 
> Note: merging free pages when a migration fails and a lower order free
> page is returned via compaction_free() is possible, but there is too much
> work.  Since the free pages are not buddy pages, it is hard to identify
> these free pages using existing PFN-based page merging algorithm.
> 
> Signed-off-by: Zi Yan <ziy@...dia.com>
> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Tested-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Tested-by: Yu Zhao <yuzhao@...gle.com>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

Thanks!