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Re: why copying files so slow in ext3



Hi,

On Sat, Dec 15, 2001 at 10:22:19PM -0800, Andrew Morton wrote:

> Let's check that I understand this.  Are you saying that
> 
> - copying a 20 megabyte file from an ext2 filesystem onto
>   a RAM disk takes 1-2 seconds.
> 
> - copying a 20 megabyte file from an ext3 filesystem onto a
>   RAM disk takes 5-6 seconds?
> 
> If this is a correct interpretation, then I'd suggest that
> something odd has happened.  The file reading paths for ext3
> are practically identical to those for ext2.

And doing a copy from ext3 to ext3 _on disk_ only takes a tiny
fraction of that for me:

[sct sisko] /tmp $ time cp testfile testfile2

real	0m0.347s
user	0m0.000s
sys	0m0.320s

I suspect that the problem is that the ramdisk is small, and has a
small journal: we may well be seeing the journal getting flushed all
the time if the journal is microscopic.  But we'd need to see more
information to be sure.

Is this timing repeatable?

Cheers,
 Stephen





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