linux-kernel - Re: [PATCH v5 2/6] memblock: Introduce bottom-up allocation mode

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Message-ID: <524454BE.4030602@gmail.com>
Date:	Thu, 26 Sep 2013 23:37:34 +0800
From:	Zhang Yanfei <zhangyanfei.yes@...il.com>
To:	Tejun Heo <tj@...nel.org>
CC:	"Rafael J . Wysocki" <rjw@...k.pl>, lenb@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>, mingo@...e.hu,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Toshi Kani <toshi.kani@...com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Thomas Renninger <trenn@...e.de>,
	Yinghai Lu <yinghai@...nel.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	isimatu.yasuaki@...fujitsu.com, izumi.taku@...fujitsu.com,
	Mel Gorman <mgorman@...e.de>, Minchan Kim <minchan@...nel.org>,
	mina86@...a86.com, gong.chen@...ux.intel.com,
	vasilis.liaskovitis@...fitbricks.com, lwoodman@...hat.com,
	Rik van Riel <riel@...hat.com>, jweiner@...hat.com,
	prarit@...hat.com, "x86@...nel.org" <x86@...nel.org>,
	linux-doc@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>, linux-acpi@...r.kernel.org,
	imtangchen@...il.com, Zhang Yanfei <zhangyanfei@...fujitsu.com>
Subject: Re: [PATCH v5 2/6] memblock: Introduce bottom-up allocation mode

Hello tejun,

Thanks for your quick comments first:)

On 09/26/2013 10:45 PM, Tejun Heo wrote:
> Hello,
> 
> On Wed, Sep 25, 2013 at 02:27:48AM +0800, Zhang Yanfei wrote:
>> +#ifdef CONFIG_MOVABLE_NODE
>> +static inline void memblock_set_bottom_up(bool enable)
>> +{
>> +	memblock.bottom_up = enable;
>> +}
>> +
>> +static inline bool memblock_bottom_up(void)
>> +{
>> +	return memblock.bottom_up;
>> +}
> 
> Can you please explain what this is for here?

OK, will do.

> 
>> +		/*
>> +		 * we always limit bottom-up allocation above the kernel,
>> +		 * but top-down allocation doesn't have the limit, so
>> +		 * retrying top-down allocation may succeed when bottom-up
>> +		 * allocation failed.
>> +		 *
>> +		 * bottom-up allocation is expected to be fail very rarely,
>> +		 * so we use WARN_ONCE() here to see the stack trace if
>> +		 * fail happens.
>> +		 */
>> +		WARN_ONCE(1, "memblock: Failed to allocate memory in bottom up "
>> +			"direction. Now try top down direction.\n");
>> +	}
> 
> You and I would know what was going on and what the consequence of the
> failure may be but the above warning message is kinda useless to a
> user / admin, right?  It doesn't really say anything meaningful.
> 

Hmmmm.. May be something like this:

WARN_ONCE(1, "Failed to allocated memory above the kernel in bottom-up,"
          "so try to allocate memory below the kernel.");

Thanks

-- 
Thanks.
Zhang Yanfei
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