cpio to ext4 seems much slower than to ext2, ext3 or xfs

[Eric Sandeen]

Richard W.M. Jones wrote:
> On Thu, Nov 12, 2009 at 09:54:12AM +0000, Daniel P. Berrange wrote:
>> On Wed, Nov 11, 2009 at 09:05:20PM +0000, Richard W.M. Jones wrote:
>>> On Wed, Nov 11, 2009 at 01:24:20PM -0600, Eric Sandeen wrote:
>>>> Anybody got actual numbers?  I don't disagree that mkfs.ext4 is slow in  
>>>> the default config, but I don't think it should be slower than mkfs.ext3  
>>>> for the same sized disks.
>>> Easy with guestfish:
>>>
>>>   $ guestfish --version
>>>   guestfish 1.0.78
>>>   $ for fs in ext2 ext3 ext4 xfs jfs ; do guestfish sparse /tmp/test.img 10G : run : echo $fs : sfdiskM /dev/sda , : time mkfs $fs /dev/sda1 ; done
>>>   ext2
>>>   elapsed time: 5.21 seconds
>>>   ext3
>>>   elapsed time: 7.87 seconds
>>>   ext4
>>>   elapsed time: 6.10 seconds
>>>   xfs
>>>   elapsed time: 0.45 seconds
>>>   jfs
>>>   elapsed time: 0.78 seconds
>>>
>>> Note that because this is using a sparsely allocated disk each write
>>> to the virtual disk is very slow.  Change 'sparse' to 'alloc' to test
>>> this with a non-sparse file-backed disk.
>> You really want to avoid using sparse files at all when doing any kind of
>> benchmark / performance tests in VMs. The combo of a sparse file store on
>> a journalling filesystem in the host, w/ virt can cause very pathelogically
>> bad I/O performance until the file has all its extents fully allocated on
>> the host FS. So the use of a sparse file may well be exagarating the real
>> difference in elapsed time between these different mkfs calls in the 
>> guest.
> 
> Again, this time backed by a 10 GB logical volume in the host, so this
> should remove pretty much all host effects:
> 
> $ for fs in ext2 ext3 ext4 xfs jfs reiserfs nilfs2 ntfs msdos btrfs hfs hfsplus gfs gfs2 ; do guestfish add /dev/mapper/vg_trick-Temp : run : zero /dev/sda : echo $fs : sfdiskM /dev/sda , : time mkfs $fs /dev/sda1 ; done


> ext2
> elapsed time: 3.48 seconds

> ext3
> elapsed time: 5.45 seconds
> ext4
> elapsed time: 5.19 seconds

so here we have ext4 slightly faster, which was the original question... ;)

(dropping caches in between might be best, too...)

> xfs
> elapsed time: 0.35 seconds
> jfs
> elapsed time: 0.66 seconds
> reiserfs
> elapsed time: 0.73 seconds
> nilfs2
> elapsed time: 0.19 seconds
> ntfs
> elapsed time: 2.33 seconds
> msdos
> elapsed time: 0.29 seconds
> btrfs
> elapsed time: 0.16 seconds
> hfs
> elapsed time: 0.44 seconds
> hfsplus
> elapsed time: 0.46 seconds
> gfs
> elapsed time: 1.60 seconds
> gfs2
> elapsed time: 3.98 seconds
> 
> I'd like to repeat my proviso: I think this test is meaningless for
> most users.

Until users have 8TB raids at home, which is not really that far off ...

-Eric

> Rich.
>