linux-kernel - Re: [RESEND PATCH] mm: align larger anonymous mappings on THP boundaries

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Date: Tue, 7 May 2024 12:14:26 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: David Hildenbrand <david@...hat.com>,
 Kefeng Wang <wangkefeng.wang@...wei.com>, Yang Shi <shy828301@...il.com>
Cc: Matthew Wilcox <willy@...radead.org>,
 Yang Shi <yang@...amperecomputing.com>, riel@...riel.com, cl@...ux.com,
 akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 Ze Zuo <zuoze1@...wei.com>
Subject: Re: [RESEND PATCH] mm: align larger anonymous mappings on THP
 boundaries

On 07/05/2024 12:13, David Hildenbrand wrote:
> 
>> https://github.com/intel/lmbench/blob/master/src/lat_mem_rd.c#L95
>>
>>> suggest. If you want to try something semi-randomly; it might be useful to rule
>>> out the arm64 contpte feature. I don't see how that would be interacting here if
>>> mTHP is disabled (is it?). But its new for 6.9 and arm64 only. Disable with
>>> ARM64_CONTPTE (needs EXPERT) at compile time.
>> I don't enabled mTHP, so it should be not related about ARM64_CONTPTE,
>> but will have a try.
> 
> cont-pte can get active if we're just lucky when allocating pages in the right
> order, correct Ryan?

No it shouldn't do; it requires the pages to be in the same folio.