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Subject: Re: [PATCH] mm/memblock:use a more appropriate order calculation when
 free memblock pages
To:     Marek Szyprowski <m.szyprowski@samsung.com>,
        Qian Cai <qcai@redhat.com>, <carver4lio@163.com>,
        <rppt@kernel.org>
CC:     <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>,
        Hailong Liu <liu.hailong6@zte.com.cn>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Linux Next Mailing List <linux-next@vger.kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
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References: <20201203152311.5272-1-carver4lio@163.com>
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From:   Jon Hunter <jonathanh@nvidia.com>
Message-ID: <3d709122-0364-5bca-9247-3f212096b389@nvidia.com>
Date:   Fri, 4 Dec 2020 17:43:21 +0000
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On 04/12/2020 16:07, Marek Szyprowski wrote:
> Hi All,
> 
> On 04.12.2020 14:42, Qian Cai wrote:
>> On Thu, 2020-12-03 at 23:23 +0800, carver4lio@163.com wrote:
>>> From: Hailong Liu <liu.hailong6@zte.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@zte.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.


FWIW, I also confirm that this is causing several 32-bit Tegra platforms
to crash on boot and reverting this fixes the problem.

Jon

-- 
nvpublic