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

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Message-ID: <da24d8bb-3723-48fa-86f4-8b24457d3556@huawei.com>
Date: Tue, 7 May 2024 21:53:51 +0800
From: Kefeng Wang <wangkefeng.wang@...wei.com>
To: David Hildenbrand <david@...hat.com>, Ryan Roberts <ryan.roberts@....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 2024/5/7 19:13, 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.

After ARM64_CONTPTE disabled, memory read latency is similar with 
ARM64_CONTPTE enabled(default 6.9-rc7), still larger than align anon 
reverted.

> 
> cont-pte can get active if we're just lucky when allocating pages in the 
> right order, correct Ryan?
>