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Re: [Xen-users] how can empty xen disk cache??

On Fri, Jul 22, 2011 at 07:11:57PM -0700, Mark Pryor wrote:
>    --------------------------------------------------------------------------
>    From: Radhya sahal <rad_cs_2006@xxxxxxxxx>
>    To: xen-users@xxxxxxxxxxxxxxxxxxx
>    Sent: Friday, July 22, 2011 5:36 PM
>    Subject: [Xen-users] how can empty xen disk cache??
>    hi
>    I am new user for xen
>    i have VM and i run java application on it ..
>    i want to empty cache for vm
>    i do that with
>    echo 3 >/proc/sys/vm/drop_caches
>    and the same command in physical machine
>    but there is not any effect
>    i think the vm have own cache in xen
>    how can empty xen disk cache??
>    thanks
>    check options in /etc/sysconfig/xendomains or (etc/default -- in debian)
>    and turn off save/restore.

I don't think the question has nothing to do with save/restore.

Dom0 does not usually cache domU disk IO, unless you're using file: backend.
Which disk backends are you using? 

tap:aio and phy: backends bypass the dom0 page cache, 
and thus those backends don't have any caching in xen dom0.

Xen hypervisor itself does not have cache of any kind.

-- Pasi

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