linux-kernel - Re: [PATCH v3 1/5] memblock: Introduce allocation direction to memblock.

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Message-ID: <52406E03.5060004@gmail.com>
Date:	Tue, 24 Sep 2013 00:36:19 +0800
From:	Zhang Yanfei <zhangyanfei.yes@...il.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Tang Chen <tangchen@...fujitsu.com>, rjw@...k.pl, lenb@...nel.org,
	tglx@...utronix.de, mingo@...e.hu, hpa@...or.com,
	akpm@...ux-foundation.org, toshi.kani@...com,
	zhangyanfei@...fujitsu.com, liwanp@...ux.vnet.ibm.com,
	trenn@...e.de, yinghai@...nel.org, jiang.liu@...wei.com,
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	linux-acpi@...r.kernel.org
Subject: Re: [PATCH v3 1/5] memblock: Introduce allocation direction to memblock.

Hello tejun,

On 09/23/2013 11:38 PM, Tejun Heo wrote:
> Hello,
> 
> Sorry about the delay.  Was traveling.

hoho~ I guess you did have a good time.

> 
> On Fri, Sep 13, 2013 at 05:30:51PM +0800, Tang Chen wrote:
>> +/* Allocation order. */
>> +#define MEMBLOCK_DIRECTION_HIGH_TO_LOW	0
>> +#define MEMBLOCK_DIRECTION_LOW_TO_HIGH	1
>> +#define MEMBLOCK_DIRECTION_DEFAULT	MEMBLOCK_DIRECTION_HIGH_TO_LOW
> 
> Can we please settle on either top_down/bottom_up or
> high_to_low/low_to_high?  The two seem to be used interchangeably in
> the patch series.  Also, it'd be more customary to use enum for things
> like above, but more on the interface below.

OK. let's use top_down/bottom_up. And using enum is also ok.

> 
>> +static inline bool memblock_direction_bottom_up(void)
>> +{
>> +	return memblock.current_direction == MEMBLOCK_DIRECTION_LOW_TO_HIGH;
>> +}
> 
> Maybe just memblock_bottom_up() would be enough?

Agreed.

> 
> Also, why not also have memblock_set_bottom_up(bool enable) as the
> 'set' interface?

hmmm, ok. So we will use memblock_set_bottom_up to replace
memblock_set_current_direction below.

> 
>>  /**
>> + * memblock_set_current_direction - Set current allocation direction to allow
>> + *                                  allocating memory from higher to lower
>> + *                                  address or from lower to higher address
>> + *
>> + * @direction: In which order to allocate memory. Could be
>> + *             MEMBLOCK_DIRECTION_{HIGH_TO_LOW|LOW_TO_HIGH}
>> + */
>> +void memblock_set_current_direction(int direction);
> 
> Function comments should go with the function definition.  Dunno what
> happened with set_current_limit but let's please not spread it.
> 
>> +void __init_memblock memblock_set_current_direction(int direction)
>> +{
>> +	if (direction != MEMBLOCK_DIRECTION_HIGH_TO_LOW &&
>> +	    direction != MEMBLOCK_DIRECTION_LOW_TO_HIGH) {
>> +		pr_warn("memblock: Failed to set allocation order. "
>> +			"Invalid order type: %d\n", direction);
>> +		return;
>> +	}
>> +
>> +	memblock.current_direction = direction;
>> +}
> 
> If set_bottom_up() style interface is used, the above will be a lot
> simpler, right?  Also, it's kinda weird to have two separate patches
> to introduce the flag and actually implement bottom up allocation.

Yeah, right, that'd be much simpler. And it is ok to put the two in
one patch.

Thanks.

> 
> Thanks.
> 


-- 
Thanks.
Zhang Yanfei
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