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Date:	Wed, 06 Apr 2011 01:23:19 +0800
From:	Coly Li <>
To:	Theodore Ts'o <>
Subject: Re: [PATCH, RFC 00/12] bigalloc patchset

On 2011年03月20日 05:28, Theodore Ts'o Wrote:
> This is an initial patchset of the bigalloc patches to ext4.  This patch
> adds support for clustered allocation, so that each bit in the ext4
> block allocation bitmap addresses a power of two number of blocks.  For
> example, if the file system is mainly going to be storing large files in
> the 4-32 megabyte range, it might make sense to set a cluster size of 1
> megabyte.  This means that each bit in the block allocaiton bitmap would
> now address 256 4k blocks, and it means that the size of the block
> bitmaps for a 2T file system shrinks from 64 megabytes to 256k.  It also
> means that a block group addresses 32 gigabytes instead of 128
> megabytes, also shrinking the amount of file system overhead for
> metadata.
> The cost is increased disk space efficiency.  Directories will consume
> 1T, as will extent tree blocks.  (I am on the fence as to whether I
> should add complexity so that in the rare case that an inode needs more
> than 344 extents --- a highly fragmented file indeed --- and need a
> second extent tree block, we can avoid allocating any cluster and
> instead use another block from the cluster used by the inode.  The
> concern is the amount of complexity this adds to the e2fsck, not just to
> the kernel.)
> To test these patches, I have used an *extremely* kludgy set of patches
> to e2fsprogs, which are attached below.  These patches need *extensive*
> revision before I would consider them clean enough suitable for
> committing into e2fsprogs, but they were sufficient for me to do the
> kernel-side changes --- mke2fs, dumpe2fs, and debugfs work.  E2fsck most
> definitely does _not_ work at this stage.
> Please comment!  I do not intend for these patches to be merged during
> the 2.6.39 merge window.  I am targetting 2.6.40, 3 months from now,
> since these patches are quite extensive.

Hi Ted,

Is it possible to open a git repo/branch for both kernel and user space tools ? So others can follow, help or provide 
performance number in time :-)



Coly Li
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