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

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Message-ID: <CADYN=9+nE=n4cXb6gDKmQqfkn97HoFShKGSpqVise=XR-aGtVw@mail.gmail.com>
Date:   Sat, 5 Dec 2020 18:09:14 +0100
From:   Anders Roxell <anders.roxell@...aro.org>
To:     Jon Hunter <jonathanh@...dia.com>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Qian Cai <qcai@...hat.com>, carver4lio@....com,
        rppt@...nel.org, Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <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>,
        linux-tegra <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH] mm/memblock:use a more appropriate order calculation when
 free memblock pages

On Fri, 4 Dec 2020 at 18:44, Jon Hunter <jonathanh@...dia.com> wrote:
>
>
> 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@....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.
>
>
> FWIW, I also confirm that this is causing several 32-bit Tegra platforms
> to crash on boot and reverting this fixes the problem.

I had the same experience on an arm64 system.

Cheers,
Anders