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

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Date:	Mon, 29 Mar 2010 17:03:39 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	michael@...erman.id.au, 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 04:31 PM, Benjamin Herrenschmidt wrote:
> On Tue, 2010-03-30 at 09:20 +1100, Michael Ellerman wrote:
>>
>> But that's my point. You shouldn't need to touch the existing API, and
>> you shouldn't need to add a new parallel API. You should just be able to
>> add the logic for doubling the array in the lmb core, and then everyone
>> gets dynamically expandable lmb. I don't see any reason why we want to
>> have two APIs.
> 
> Ack.
ok, we can merge them later.
> 
>>>> It seems to me that rather than adding these "special" routines that
>>>> check for enough space on the way in, instead you should be checking in
>>>> lmb_add_region() - which is where AFAICS all allocs/frees/reserves
>>>> eventually end up if they need to insert a new region.
>>>
>>> later i prefer to replace lmb_alloc with find_lmb_area + reserve_lmb.
>>
>> Why? The existing code has been working for years and is well tested? 
> 
> I still don't totally understand why he needs a find_lmb_area()
> anyways. 
> 
> It might be justified ... or not. I just want it to be better
> documented.


current changelog for that

------------------

Subject: [PATCH 6/31] lmb: Add lmb_find_area()

It will try find area according with size/align in specified range (start, end).

Need use it find correct buffer for new lmb.reserved.region.

also make it more easy for x86 to use lmb.
x86 early_res is using find/reserve pattern instead of alloc.

lmb_find_area() will honor goal

When we need temporary buff for range array etc for range work, if We are using
lmb_alloc(), We will need to add some post fix code for buffer that is used
by range array, because it is in the lmb.reserved already.

----------------

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.

Thanks

Yinghai
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