Re: Trace Disk I/O per guest domain!

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Tue, Sep 01, 2009 at 12:19:33AM +0530, Ata Bohra wrote:
> 
> Dear All, 
> 
>  
> 
> I am trying to trace all the disk I/O accesses made by the xen guest domains to dom0 domain. I would request for critics or comments in doing the same. Its easy to run "iostat -x" on all domains and dom0 to get the disk i/o utilization stats, but I am just looking if there can be any other way than running this utility in all domUs but using simply dom0 to get all guest domain stats along with dom0 accesses (different from domUs) also. 
> 

The way we did it (VirtualIron) in the past to narrow down a specific problem [1] was to
instrument the blkback.c. Each time a bio was submitted we would add it to a list
along with the domid. And obviously in the bio_endio callback this entry would be
removed.

>From there on, you can add SysFS interfaces to keep track of how much I/O is going
from/to each domain.

[1]: http://lists.xensource.com/archives/html/xen-devel/2008-12/msg00222.html

Oh way, you said "utility." Umm.. blktrace, but that still doesn't give you the
granularity you want.