[dm-devel] Re: Regarding dm-ioband tests
Ryo Tsuruta
ryov at valinux.co.jp
Thu Sep 10 03:45:47 UTC 2009
Hi Vivek,
Vivek Goyal <vgoyal at redhat.com> wrote:
> > In addition,
> > there are devices which doesn't use standard IO schedulers, and
> > dm-ioband can work on even such devices.
>
> This is a interesting use case. Few thoughts.
>
> - Can't io scheduling mechanism of these devices make use of elevator and
> elevator fair queuing interfaces to take advantage of io controlling
> mechanism. It should not be too difficult. Look at noop. It has
> just 131 lines of code and it now supports hierarchical io scheduling.
>
> This will come with request queue and its merging and plug/unplug
> mechanism. Is that an issue?
>
> - If not, then yes, for these corner cases, io scheduler based controller
> does not work as it is.
I have a extreme fast SSD and its device driver provides its own
make_request_fn(). So the device driver intercepts IO requests and the
subsequent processes are done within it.
Thanks,
Ryo Tsuruta
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