* ext4 allocator
@ 2010-01-25 21:14 Alberich de megres
2010-01-25 21:37 ` Andreas Dilger
0 siblings, 1 reply; 3+ messages in thread
From: Alberich de megres @ 2010-01-25 21:14 UTC (permalink / raw)
To: linux-fsdevel
Hi!!
I'm studyng ext4 code, and i got a doubt on a situation:
Supposing a 4K page size, and a fs with 8K.. when we are filling page info,:
{ 4K page }{ 4K page }{ 4K page }{ 4K page }
[ group 0 bitmap ] [ group 0 buddy ]
Clearly bitmap and buddy info don't fits on a single page, but e4b
structure saves only one page address.
How mb allocator menages this situation??
Thanks!!!
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: ext4 allocator
2010-01-25 21:14 ext4 allocator Alberich de megres
@ 2010-01-25 21:37 ` Andreas Dilger
2010-01-25 22:44 ` Alberich de megres
0 siblings, 1 reply; 3+ messages in thread
From: Andreas Dilger @ 2010-01-25 21:37 UTC (permalink / raw)
To: Alberich de megres; +Cc: linux-fsdevel
On 2010-01-25, at 14:14, Alberich de megres wrote:
> I'm studyng ext4 code, and i got a doubt on a situation:
>
> Supposing a 4K page size, and a fs with 8K.. when we are filling
> page info,:
>
> { 4K page }{ 4K page }{ 4K page }{ 4K page }
> [ group 0 bitmap ][ group 0 buddy ]
>
> Clearly bitmap and buddy info don't fits on a single page, but e4b
> structure saves only one page address.
>
> How mb allocator menages this situation??
ext4, and the Linux VM/block layer in general, do not support disk
block size larger than the page size. That has been a restriction for
a long time already, and there have been various patches/proposals to
fix that, but nothing that ever made it into the mainline kernel.
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: ext4 allocator
2010-01-25 21:37 ` Andreas Dilger
@ 2010-01-25 22:44 ` Alberich de megres
0 siblings, 0 replies; 3+ messages in thread
From: Alberich de megres @ 2010-01-25 22:44 UTC (permalink / raw)
To: Andreas Dilger; +Cc: linux-fsdevel
Wow, how newbie i am...
Thanks man!!
On Mon, Jan 25, 2010 at 10:37 PM, Andreas Dilger <adilger@sun.com> wrote:
> On 2010-01-25, at 14:14, Alberich de megres wrote:
>>
>> I'm studyng ext4 code, and i got a doubt on a situation:
>>
>> Supposing a 4K page size, and a fs with 8K.. when we are filling page
>> info,:
>>
>> { 4K page }{ 4K page }{ 4K page }{ 4K page }
>> [ group 0 bitmap ][ group 0 buddy ]
>>
>> Clearly bitmap and buddy info don't fits on a single page, but e4b
>> structure saves only one page address.
>>
>> How mb allocator menages this situation??
>
>
> ext4, and the Linux VM/block layer in general, do not support disk block
> size larger than the page size. That has been a restriction for a long time
> already, and there have been various patches/proposals to fix that, but
> nothing that ever made it into the mainline kernel.
>
> Cheers, Andreas
> --
> Andreas Dilger
> Sr. Staff Engineer, Lustre Group
> Sun Microsystems of Canada, Inc.
>
>
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^ permalink raw reply [flat|nested] 3+ messages in thread
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2010-01-25 21:14 ext4 allocator Alberich de megres
2010-01-25 21:37 ` Andreas Dilger
2010-01-25 22:44 ` Alberich de megres
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