linux-kernel - Re: [PATCH v3 4/5] powerpc/mm: restore top-down allocation when using movable

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Message-Id: <20160926204839.bugxlsyd4p3or5p2@arbab-laptop>
Date:   Mon, 26 Sep 2016 15:48:40 -0500
From:   Reza Arbab <arbab@...ux.vnet.ibm.com>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Bharata B Rao <bharata@...ux.vnet.ibm.com>,
        Nathan Fontenot <nfont@...ux.vnet.ibm.com>,
        Stewart Smith <stewart@...ux.vnet.ibm.com>,
        Alistair Popple <apopple@....ibm.com>,
        Balbir Singh <bsingharora@...il.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, devicetree@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v3 4/5] powerpc/mm: restore top-down allocation when
 using movable_node

On Mon, Sep 26, 2016 at 09:17:43PM +0530, Aneesh Kumar K.V wrote:
>> +	/* bottom-up allocation may have been set by movable_node */
>> +	memblock_set_bottom_up(false);
>> +
>
>By then we have done few memblock allocation right ?

Yes, some allocations do occur while bottom-up is set.

>IMHO, we should do this early enough in prom.c after we do 
>parse_early_param, with a comment there explaining that, we don't 
>really support hotplug memblock and when we do that, this should be 
>moved to a place where we can handle memblock allocation such that we 
>avoid spreading memblock allocation to movable node.

Sure, we can do it earlier. The only consideration is that any potential 
calls to memblock_mark_hotplug() happen before we reset to top-down.  
Since we don't do that at all on power, the call can go anywhere.

-- 
Reza Arbab