Re: Loopback Performance (Was Re: Disk naming)

[Anthony Liguori <aliguori@us.ibm.com>]

Mark Williamson wrote:

>On Friday 15 April 2005 23:11, Anthony Liguori wrote:
>  
>
>I'm sorry but I don't follow this.  The inodes for the filesystem inside it 
>only need to be looked up by the guest filesystem driver.  The inode for the 
>disk file only needs to be looked up once in dom0 when the file is opened 
>(the metadata will then be cached).  Am I missing something?
>  
>
I meant looking up the data blocks in the inode.  You may be hitting 
triple-indirect blocks twice.

I don't know enough about the kernel level caching to say anything 
definitive.  I do have some ideas who to ask though.

Regards,
Anthony Liguori

>The data you've collected are interesting though.  I wonder if searching the 
>LKML archives might yield any interesting discussion about the loop device's 
>behaviour.
>
>Cheers,
>Mark
>  
>