[Xen-users] ionice command to set i/o priorities for domUs

[Israel Garcia <igalvarez@xxxxxxxxx>]

Hi, I have xen on a debian lenny with more then 20 VM. The supermicro
server has a raid10 with a good performance, but I have IO issues when
one VM is making backup, it affects the performance of the other VMs.
I've setup cpus, vcpus, sched-credit between dom0 and domUs as doc
recommended, but I'm still facing IO problems. So I found a way to
mediate disk access with ionice from the dom0. I mean changing
priority to domUs PID. See below more details.

I'm using CFQ scheduler
dom0:~#  cat /sys/block/[sh]d[a-z]*/queue/scheduler
noop anticipatory deadline [cfq]
noop anticipatory deadline [cfq]

It's  a part of ps regarding block devices:
15747 ?        S<     0:00  \_ [blkback.64.xvda]
15748 ?        S<     0:54  \_ [blkback.64.xvda]
20353 ?        S<     0:00  \_ [blkback.71.xvda]
20354 ?        S<     0:05  \_ [blkback.71.xvda]
 2361 ?        S<     0:00  \_ [blkback.112.xvd]
 2362 ?        S<     0:15  \_ [blkback.112.xvd]
26596 ?        S<     0:00  \_ [blkback.122.xvd]
26597 ?        S<     0:00  \_ [blkback.122.xvd]
27203 ?        S<     0:00  \_ [blkback.123.xvd]
27204 ?        S<     0:00  \_ [blkback.123.xvd]

Finally, I change these PIDs with ionice and make several tests but
I'm still confuse with the results. My question:

Does anybody on this list use ionice to mediate disk priority to disk
intense domU with ionice from dom0?

appreciate your help.

-- 
Regards;
Israel Garcia

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