[Xen-devel] Is disk scheduler in VM useful?

[smiler <xlinghust@xxxxxxxxx>]

Hi all,

I do the experiment in Xen 4.0.1 with Linux 2.6.31.8 using blktap AIO.  Two
sequential read applications (sysbench) run on a VM. I compare the
performance of application under AS, noop and CFQ in the domU, respectively
(disk scheduler of dom0 is CFQ). The results of three schedulers are almost
the same. I did not know why AS does not work for sequentail access
applications,  even the performance of AS is same as noop in two sequential
applications. In the physical machine, the as is better than noop, cfq when
running two sequential applications. 
Does this mean that scheduling I/O requests in VM is not useful?




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