linux-ext4 - Re: Ext4 devel interlock meeting minutes (April 23, 2007)

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Date:	Tue, 01 May 2007 17:38:53 +0530
From:	Kalpak Shah <kalpak@...sterfs.com>
To:	Aneesh Kumar <aneesh.kumar@...il.com>
Cc:	Avantika Mathur <mathur@...ux.vnet.ibm.com>,
	linux-ext4@...r.kernel.org
Subject: Re: Ext4 devel interlock meeting minutes (April 23, 2007)

On Mon, 2007-04-30 at 16:36 +0530, Aneesh Kumar wrote:
> On 4/24/07, Avantika Mathur <mathur@...ux.vnet.ibm.com> wrote:
> > Ext4 Developer Interlock Call: 04/23/2007 Meeting Minutes
> >
> > TESTING
> > - extents testing
> >     - Discussed methods for testing extents on highly fragmented
> > filesystems.
> >     - Jose will look into possible tests, including perhaps using the
> > 'aged' option in FFSB
> >     - Ted suggested creating a mountoption that creates a bad block
> > allocator which it jumps to a new block group every 8 blocks.  This
> > would force a very large number of extents, and may be a good test for
> > extents.
> 
> 
> What i am doing for creating a large number of extents is
> 
> dd if=/dev/zero of=myfile count=10
> seek=20
> while [ 1 ]; do dd if=/dev/zero of=myfile count=10 seek=$seek;
> seek=`expr $seek + 20`; done
> 
> 

I had written a simple tool "bitmap_manip" with which you can actually
manipulate the number of free chunks and their sizes in a filesystem. It
uses libext2fs to set the bits in block bitmaps thereby leaving the
desired free extents. I had written it to test the allocators
performance. 

It can be used as:
 ./bitmap_manip /dev/sda9 1MA 4 16K 1 12K 3 8K 4 4K 6
 
This will leave only 1 16K chunk, 3 12K chunks, .... free in the
filesystem. "1MA" 4 will get us 4 1Mb free ALIGNED chunks.

It isn't very beautiful code since it was only used for testing but
maybe it can help.

Thanks,
Kalpak.

> -aneesh
> -
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View attachment "bitmap_manip.c" of type "text/x-csrc" (5075 bytes)