linux-ext4 - Re: [RFC] enable ext4 allocate blocks across group boundary

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Message-ID: <CAGBYx2YESmmVxr+9=+sPgyepdm=rW2fKGVrp=RGFe=yYOgoN9A@mail.gmail.com>
Date:	Thu, 15 Mar 2012 10:57:49 +0800
From:	Yongqiang Yang <xiaoqiangnk@...il.com>
To:	Robin Dong <hao.bigrat@...il.com>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [RFC] enable ext4 allocate blocks across group boundary

2012/3/15 Robin Dong <hao.bigrat@...il.com>:
> 在 2012年3月15日 上午8:52，Yongqiang Yang <xiaoqiangnk@...il.com> 写道：
>> Hello List,
>>
>> Here is a proposal to enable ext4 allocate blocks across group boundary.
>>
>> Now ext4 allocates blocks within a single block group by locking a
>> group.   Flex_bg puts metadata blocks together, as a result,it
>> enlarges contiguous blocks.  So we can enable ext4 allocate blocks
>> within a flex block group. Inode allocation takes group lock as block
>> allocation,  I am not sure if we should allocate inode within single
>> group as before.
>>
>> If we do this, then the new group boundary will be flex block group
>> boundary.  I am not sure if it is worth doing.
>
> IMO, since the max size of one ext4-extent is just 128MB, maybe a
> contiguous space
> beyond a single block group can not be used efficiently.
I do not think maximum of extent size limits the value of block
allocation across group boundary.

Actually, maximum of contiguous blocks is determined by block
allocation strategy(multi block allocation, preallocation, group
selection ...) rather than others.   Given that ext4 is indirect
mapped and uses current block allocation strategy, contiguous blocks
is still same.

Yongqiang.
>
>>
>>
>> Any ideas?
>>
>> --
>> Best Wishes
>> Yongqiang Yang
>> --
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>
>
>
> --
> --
> Best Regard
> Robin Dong



-- 
Best Wishes
Yongqiang Yang
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