Jürgen Keil wrote:> Is it true (it seems so...) that the linux dom0 pv block backend driver
> is bypassing the buffer / page cache of dom0 [*]?
> And the solaris dom0 block backend driver doesn''t?
>
> Are there any technical reasons why linux doesn''t cache in dom0?
>
> Is it a bug or feature that solaris does cache in dom0?
>
> Well, a positive effect of solaris dom0 cacheing seems to be
> that /boot/solaris/bin/create_ramdisk inside a solaris domU is
> much faster when running on a solaris dom0 than on a linux dom0.
> E.g. (8G - 1G) dom0 ubuntu amd64 + 1G solaris amd64 PV domU
> needs ~40 seconds for create_ramdisk in domU, while
> (4G - 0.5G) dom0 solaris amd64 + .5G solaris amd64 PV domU
> needs ~22 seconds for create_ramdisk in domU.
>
>
> [*]
http://lists.xensource.com/archives/html/xen-devel/2005-05/msg01167.html
>
Heres''s Stu''s answer...
"the Solaris backend caches deliberately since we are
emulating a disk with a write buffer, and we support
the flush cache operation to ensure that front end
software has a way to guarantee that written data is
on stable storage. In the same way that issuing a
flush to a disk with a write cache will. "
MRJ