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

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Message-ID: <20130926144516.GD3482@htj.dyndns.org>
Date:	Thu, 26 Sep 2013 10:45:16 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Zhang Yanfei <zhangyanfei.yes@...il.com>
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,

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?

> +		/*
> +		 * 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.

Thanks.

-- 
tejun
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