linux-kernel - Re: [PATCH] mm/memblock:use a more appropriate order calculation when free memblock pages

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Date:   Fri, 4 Dec 2020 17:07:50 +0100
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Qian Cai <qcai@...hat.com>, carver4lio@....com, rppt@...nel.org
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Hailong Liu <liu.hailong6@....com.cn>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH] mm/memblock:use a more appropriate order calculation
 when free memblock pages

Hi All,

On 04.12.2020 14:42, Qian Cai wrote:
> On Thu, 2020-12-03 at 23:23 +0800, carver4lio@....com wrote:
>> From: Hailong Liu <liu.hailong6@....com.cn>
>>
>> When system in the booting stage, pages span from [start, end] of a memblock
>> are freed to buddy in a order as large as possible (less than MAX_ORDER) at
>> first, then decrease gradually to a proper order(less than end) in a loop.
>>
>> However, *min(MAX_ORDER - 1UL, __ffs(start))* can not get the largest order
>> in some cases.
>> Instead, *__ffs(end - start)* may be more appropriate and meaningful.
>>
>> Signed-off-by: Hailong Liu <liu.hailong6@....com.cn>
> Reverting this commit on the top of today's linux-next fixed boot crashes on
> multiple NUMA systems.

I confirm. Reverting commit 4df001639c84 ("mm/memblock: use a more 
appropriate order calculation when free memblock pages") on top of linux 
next-20201204 fixed booting of my ARM32bit test systems.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland