linux-kernel - Re: [PATCH 07/31] lmb: Add reserve_lmb/free

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Message-ID: <4BB1A0EA.8050305@kernel.org>
Date:	Mon, 29 Mar 2010 23:57:46 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	michael@...erman.id.au
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 07/31] lmb: Add reserve_lmb/free_lmb

On 03/29/2010 11:46 PM, Michael Ellerman wrote:
> On Mon, 2010-03-29 at 23:12 -0700, Yinghai Lu wrote:
>> On 03/29/2010 10:26 PM, Benjamin Herrenschmidt wrote:
>>> On Mon, 2010-03-29 at 17:03 -0700, Yinghai Lu wrote:
>>>>
>>>> in short: It could make us to avoid use the range that we are going to
>>>> reserve,
>>>>       when we try to get new position new lmb.reserved.region. 
>>>
>>> I'm not too sure I follow you. For the resizing, I would just basically
>>> call a low level variant of alloc (__lmb_alloc ?) that explicitely
>>> doesn't honor the total-2 "reserved" entries in the array.
>>
>> 1. you want to reserve rangeA
>> 2. before that will check if region array is big enough,
>> 3. if region is not big enough, will call lmb_alloc to get new range.
>>    lmb_alloc could return rangB that is overlapped with rangeA
> 
> So instead you do it the other way.
> 
> 1. you want to reserve rangeA
> 2. you reserve rangeA
> 3. if reserving rangeA consumed a slot in the array then you check if
> you have at least two free slots. If not you realloc. You don't need any
> special tricks because you have space to lmb_alloc() a new area and move
> everything over.

so that is check it later. should work.

one less find_lmb_area user.

Thanks

Yinghai
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