Message-ID: <5240731B.9070906@gmail.com>
Date: Tue, 24 Sep 2013 00:58:03 +0800
From: Zhang Yanfei <zhangyanfei.yes@gmail.com>
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To: Tejun Heo <tj@kernel.org>
CC: Tang Chen <tangchen@cn.fujitsu.com>, rjw@sisk.pl, lenb@kernel.org,
        tglx@linutronix.de, mingo@elte.hu, hpa@zytor.com,
        akpm@linux-foundation.org, toshi.kani@hp.com,
        zhangyanfei@cn.fujitsu.com, liwanp@linux.vnet.ibm.com, trenn@suse.de,
        yinghai@kernel.org, jiang.liu@huawei.com, wency@cn.fujitsu.com,
        laijs@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com,
        izumi.taku@jp.fujitsu.com, mgorman@suse.de, minchan@kernel.org,
        mina86@mina86.com, gong.chen@linux.intel.com,
        vasilis.liaskovitis@profitbricks.com, lwoodman@redhat.com,
        riel@redhat.com, jweiner@redhat.com, prarit@redhat.com, x86@kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-acpi@vger.kernel.org
Subject: Re: [PATCH v3 5/5] mem-hotplug: Introduce movablenode boot option
 to control memblock allocation direction.
References: <1379064655-20874-1-git-send-email-tangchen@cn.fujitsu.com> <1379064655-20874-6-git-send-email-tangchen@cn.fujitsu.com> <20130923155713.GF14547@htj.dyndns.org>
In-Reply-To: <20130923155713.GF14547@htj.dyndns.org>
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Hello tejun,

On 09/23/2013 11:57 PM, Tejun Heo wrote:
> Hello,
> 
> On Fri, Sep 13, 2013 at 05:30:55PM +0800, Tang Chen wrote:
>> +#ifdef CONFIG_MOVABLE_NODE
>> +	if (movablenode_enable_srat) {
>> +		/*
>> +		 * When ACPI SRAT is parsed, which is done in initmem_init(),
>> +		 * set memblock back to the default behavior.
>> +		 */
>> +		memblock_set_current_direction(MEMBLOCK_DIRECTION_DEFAULT);
>> +	}
>> +#endif /* CONFIG_MOVABLE_NODE */
> 
> It's kinda weird to have ifdef around the above when all the actual
> code would be compiled and linked regardless of the above ifdef.
> Wouldn't it make more sense to conditionalize
> memblock_direction_bottom_up() so that it's constant false to allow
> the compiler to drop unnecessary code?

you mean we define memblock_set_bottom_up and memblock_bottom_up like below:

#ifdef CONFIG_MOVABLE_NODE
void memblock_set_bottom_up(bool enable)
{
        /* do something */
}

bool memblock_bottom_up()
{
        return  direction == bottom_up;
}
#else
void memblock_set_bottom_up(bool enable)
{
        /* empty */
}

bool memblock_bottom_up()
{
        return false;
}
#endif

right?

thanks.

> 
> Thanks.
> 


-- 
Thanks.
Zhang Yanfei
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